WorldWideScience

Sample records for dynamic clustered distribution

  1. Dynamical quorum sensing and clustering dynamics in a population of spatially distributed active rotators

    Science.gov (United States)

    Sakaguchi, Hidetsugu; Maeyama, Satomi

    2013-02-01

    A model of clustering dynamics is proposed for a population of spatially distributed active rotators. A transition from excitable to oscillatory dynamics is induced by the increase of the local density of active rotators. It is interpreted as dynamical quorum sensing. In the oscillation regime, phase waves propagate without decay, which generates an effectively long-range interaction in the clustering dynamics. The clustering process becomes facilitated and only one dominant cluster appears rapidly as a result of the dynamical quorum sensing. An exact localized solution is found to a simplified model equation, and the competitive dynamics between two localized states is studied numerically.

  2. Dynamical Mass Measurements of Contaminated Galaxy Clusters Using Support Distribution Machines

    Science.gov (United States)

    Ntampaka, Michelle; Trac, Hy; Sutherland, Dougal; Fromenteau, Sebastien; Poczos, Barnabas; Schneider, Jeff

    2018-01-01

    We study dynamical mass measurements of galaxy clusters contaminated by interlopers and show that a modern machine learning (ML) algorithm can predict masses by better than a factor of two compared to a standard scaling relation approach. We create two mock catalogs from Multidark’s publicly available N-body MDPL1 simulation, one with perfect galaxy cluster membership infor- mation and the other where a simple cylindrical cut around the cluster center allows interlopers to contaminate the clusters. In the standard approach, we use a power-law scaling relation to infer cluster mass from galaxy line-of-sight (LOS) velocity dispersion. Assuming perfect membership knowledge, this unrealistic case produces a wide fractional mass error distribution, with a width E=0.87. Interlopers introduce additional scatter, significantly widening the error distribution further (E=2.13). We employ the support distribution machine (SDM) class of algorithms to learn from distributions of data to predict single values. Applied to distributions of galaxy observables such as LOS velocity and projected distance from the cluster center, SDM yields better than a factor-of-two improvement (E=0.67) for the contaminated case. Remarkably, SDM applied to contaminated clusters is better able to recover masses than even the scaling relation approach applied to uncon- taminated clusters. We show that the SDM method more accurately reproduces the cluster mass function, making it a valuable tool for employing cluster observations to evaluate cosmological models.

  3. Energy Efficient Cooperative Spectrum Sensing in Cognitive Radio Networks Using Distributed Dynamic Load Balanced Clustering Scheme

    Directory of Open Access Journals (Sweden)

    Muthukkumar R.

    2017-04-01

    Full Text Available Cognitive Radio (CR is a promising and potential technique to enable secondary users (SUs or unlicenced users to exploit the unused spectrum resources effectively possessed by primary users (PUs or licenced users. The proven clustering approach is used to organize nodes in the network into the logical groups to attain energy efficiency, network scalability, and stability for improving the sensing accuracy in CR through cooperative spectrum sensing (CSS. In this paper, a distributed dynamic load balanced clustering (DDLBC algorithm is proposed. In this algorithm, each member in the cluster is to calculate the cooperative gain, residual energy, distance, and sensing cost from the neighboring clusters to perform the optimal decision. Each member in a cluster participates in selecting a cluster head (CH through cooperative gain, and residual energy that minimises network energy consumption and enhances the channel sensing. First, we form the number of clusters using the Markov decision process (MDP model to reduce the energy consumption in a network. In this algorithm, CR users effectively utilize the PUs reporting time slots of unavailability. The simulation results reveal that the clusters convergence, energy efficiency, and accuracy of channel sensing increased considerably by using the proposed algorithm.

  4. Energy Efficient Cooperative Spectrum Sensing in Cognitive Radio Networks Using Distributed Dynamic Load Balanced Clustering Scheme

    Directory of Open Access Journals (Sweden)

    Muthukkumar R.

    2016-07-01

    Full Text Available Cognitive Radio (CR is a promising and potential technique to enable secondary users (SUs or unlicenced users to exploit the unused spectrum resources effectively possessed by primary users (PUs or licenced users. The proven clustering approach is used to organize nodes in the network into the logical groups to attain energy efficiency, network scalability, and stability for improving the sensing accuracy in CR through cooperative spectrum sensing (CSS. In this paper, a distributed dynamic load balanced clustering (DDLBC algorithm is proposed. In this algorithm, each member in the cluster is to calculate the cooperative gain, residual energy, distance, and sensing cost from the neighboring clusters to perform the optimal decision. Each member in a cluster participates in selecting a cluster head (CH through cooperative gain, and residual energy that minimises network energy consumption and enhances the channel sensing. First, we form the number of clusters using the Markov decision process (MDP model to reduce the energy consumption in a network. In this algorithm, CR users effectively utilize the PUs reporting time slots of unavailability. The simulation results reveal that the clusters convergence, energy efficiency, and accuracy of channel sensing increased considerably by using the proposed algorithm.

  5. A Comparison of Alternative Distributed Dynamic Cluster Formation Techniques for Industrial Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Mohammad Gholami

    2016-01-01

    Full Text Available In this paper, we investigate alternative distributed clustering techniques for wireless sensor node tracking in an industrial environment. The research builds on extant work on wireless sensor node clustering by reporting on: (1 the development of a novel distributed management approach for tracking mobile nodes in an industrial wireless sensor network; and (2 an objective comparison of alternative cluster management approaches for wireless sensor networks. To perform this comparison, we focus on two main clustering approaches proposed in the literature: pre-defined clusters and ad hoc clusters. These approaches are compared in the context of their reconfigurability: more specifically, we investigate the trade-off between the cost and the effectiveness of competing strategies aimed at adapting to changes in the sensing environment. To support this work, we introduce three new metrics: a cost/efficiency measure, a performance measure, and a resource consumption measure. The results of our experiments show that ad hoc clusters adapt more readily to changes in the sensing environment, but this higher level of adaptability is at the cost of overall efficiency.

  6. A Comparison of Alternative Distributed Dynamic Cluster Formation Techniques for Industrial Wireless Sensor Networks.

    Science.gov (United States)

    Gholami, Mohammad; Brennan, Robert W

    2016-01-06

    In this paper, we investigate alternative distributed clustering techniques for wireless sensor node tracking in an industrial environment. The research builds on extant work on wireless sensor node clustering by reporting on: (1) the development of a novel distributed management approach for tracking mobile nodes in an industrial wireless sensor network; and (2) an objective comparison of alternative cluster management approaches for wireless sensor networks. To perform this comparison, we focus on two main clustering approaches proposed in the literature: pre-defined clusters and ad hoc clusters. These approaches are compared in the context of their reconfigurability: more specifically, we investigate the trade-off between the cost and the effectiveness of competing strategies aimed at adapting to changes in the sensing environment. To support this work, we introduce three new metrics: a cost/efficiency measure, a performance measure, and a resource consumption measure. The results of our experiments show that ad hoc clusters adapt more readily to changes in the sensing environment, but this higher level of adaptability is at the cost of overall efficiency.

  7. Introduction to cluster dynamics

    CERN Document Server

    Reinhard, Paul-Gerhard

    2008-01-01

    Clusters as mesoscopic particles represent an intermediate state of matter between single atoms and solid material. The tendency to miniaturise technical objects requires knowledge about systems which contain a ""small"" number of atoms or molecules only. This is all the more true for dynamical aspects, particularly in relation to the qick development of laser technology and femtosecond spectroscopy. Here, for the first time is a highly qualitative introduction to cluster physics. With its emphasis on cluster dynamics, this will be vital to everyone involved in this interdisciplinary subje

  8. The Business Cluster's Distribution e-Channels

    OpenAIRE

    Milan Davidovic

    2011-01-01

    The business cluster cooperative potential and business capability improvement are dependent on e-business implementation and business model change dynamics in cluster and his members based in new and existing distribution channels, customer relationships management and supplychain integration. In this work analyse cluster’s e-business models, e-commerce forms and distribution e-channels for three business cases: when cluster members are oriented on own business, on cooperative’s project or c...

  9. Flexibility dynamics in clusters of residential demand response and distributed generation

    NARCIS (Netherlands)

    MacDougall, P.A.; Kok, J.K.; Warmer, C.; Roossien, B.

    2013-01-01

    Supply and demand response is a untapped resource in the current electrical system. However little work has been done to investigate the dynamics of utilizing such flexibility as well as the potential effects it could have on the infrastructure. This paper provides a starting point to seeing the

  10. Equilibrium stochastic dynamics of Poisson cluster ensembles

    Directory of Open Access Journals (Sweden)

    L.Bogachev

    2008-06-01

    Full Text Available The distribution μ of a Poisson cluster process in Χ=Rd (with n-point clusters is studied via the projection of an auxiliary Poisson measure in the space of configurations in Χn, with the intensity measure being the convolution of the background intensity (of cluster centres with the probability distribution of a generic cluster. We show that μ is quasi-invariant with respect to the group of compactly supported diffeomorphisms of Χ, and prove an integration by parts formula for μ. The corresponding equilibrium stochastic dynamics is then constructed using the method of Dirichlet forms.

  11. Privacy-preserving distributed clustering

    DEFF Research Database (Denmark)

    Erkin, Zekeriya; Veugen, Thijs; Toft, Tomas

    2013-01-01

    by taking the distributed structure of the system into account and improving the efficiency in terms of computation and communication by data packing. While our construction can be easily adjusted to a centralized or a distributed computing model, we rely on a set of particular users that help the service...... for distributed clustering that limits information leakage to the untrusted service provider that performs the clustering. To achieve this goal, we rely on cryptographic techniques, in particular homomorphic encryption, and further improve the state of the art of processing encrypted data in terms of efficiency...... provider with computations. Experimental results clearly indicate that the work we present is an efficient way of deploying a privacy-preserving clustering algorithm in a distributed manner....

  12. Exploring the Internal Dynamics of Globular Clusters

    Science.gov (United States)

    Watkins, Laura L.; van der Marel, Roeland; Bellini, Andrea; Luetzgendorf, Nora; HSTPROMO Collaboration

    2018-01-01

    Exploring the Internal Dynamics of Globular ClustersThe formation histories and structural properties of globular clusters are imprinted on their internal dynamics. Energy equipartition results in velocity differences for stars of different mass, and leads to mass segregation, which results in different spatial distributions for stars of different mass. Intermediate-mass black holes significantly increase the velocity dispersions at the centres of clusters. By combining accurate measurements of their internal kinematics with state-of-the-art dynamical models, we can characterise both the velocity dispersion and mass profiles of clusters, tease apart the different effects, and understand how clusters may have formed and evolved.Using proper motions from the Hubble Space Telescope Proper Motion (HSTPROMO) Collaboration for a set of 22 Milky Way globular clusters, and our discrete dynamical modelling techniques designed to work with large, high-quality datasets, we are studying a variety of internal cluster properties. We will present the results of theoretical work on simulated clusters that demonstrates the efficacy of our approach, and preliminary results from application to real clusters.

  13. Dynamics of the Sgr A* cluster

    NARCIS (Netherlands)

    Romanowsky, AJ; Kochanek, CS; Dieters, S; Fuchs, B; Just, A; Spurzem, R; Wielen, R

    2001-01-01

    We model the dynamics of the star cluster around Sgr A* using a spherical potential and an arbitrary two-integral distribution function in order to fully include the uncertainties created by orbital anisotropy. Given spatial and kinematical data for the stars, we find the best-fit parameters of the

  14. Epistemic communities and cluster dynamics

    DEFF Research Database (Denmark)

    Håkanson, Lars

    2003-01-01

    This paper questions the prevailing notions that firms within industrial clusters have privi-leged access to `tacit knowledge' that is unavailable - or available only at high cost - to firms located elsewhere, and that such access provides competitive advantages that help to explain the growth...... and development of both firms and regions. It outlines a model of cluster dynam-ics emphasizing two mutually interdependent processes: the concentration of specialized and complementary epistemic communities, on the one hand, and entrepreneurship and a high rate of new firm formation on the other....

  15. Overlapping clusters for distributed computation.

    Energy Technology Data Exchange (ETDEWEB)

    Mirrokni, Vahab (Google Research, New York, NY); Andersen, Reid (Microsoft Corporation, Redmond, WA); Gleich, David F.

    2010-11-01

    Scalable, distributed algorithms must address communication problems. We investigate overlapping clusters, or vertex partitions that intersect, for graph computations. This setup stores more of the graph than required but then affords the ease of implementation of vertex partitioned algorithms. Our hope is that this technique allows us to reduce communication in a computation on a distributed graph. The motivation above draws on recent work in communication avoiding algorithms. Mohiyuddin et al. (SC09) design a matrix-powers kernel that gives rise to an overlapping partition. Fritzsche et al. (CSC2009) develop an overlapping clustering for a Schwarz method. Both techniques extend an initial partitioning with overlap. Our procedure generates overlap directly. Indeed, Schwarz methods are commonly used to capitalize on overlap. Elsewhere, overlapping communities (Ahn et al, Nature 2009; Mishra et al. WAW2007) are now a popular model of structure in social networks. These have long been studied in statistics (Cole and Wishart, CompJ 1970). We present two types of results: (i) an estimated swapping probability {rho}{infinity}; and (ii) the communication volume of a parallel PageRank solution (link-following {alpha} = 0.85) using an additive Schwarz method. The volume ratio is the amount of extra storage for the overlap (2 means we store the graph twice). Below, as the ratio increases, the swapping probability and PageRank communication volume decreases.

  16. Dynamic of Faceted Colloidal Clusters

    Science.gov (United States)

    Sindoro, Melinda; Jee, Ah-Young; Yu, Changqian; Granick, Steve

    2014-03-01

    We study the emulsion induced clustering of faceted metal organic frameworks (MOFs) and their dynamics. Our approach to anisotropic building block is through the rational synthesis of water stable and highly uniform MOFs. This generates colloidal-sized MOFs of defined polyhedral shape with tunable size in micrometer range that are suitable for in situ imaging. The 3D clusters formations are promoted by hydrophilic MOFs particles confined in aqueous droplets of binary water-lutidine mixture at transition temperature. Below this temperature, the water droplet decreases in volume due to one phase mixing with lutidine which forces the N-mers of faceted particles to aggregate in close contact. We compare the faceted clusters formed to those made of spherical particles in term of the building block sphericity. Other focus of our study involves the dynamic of the clusters. We found that, unlike spherical clusters, these faceted N-mers are highly stable on large scale of temperature due to their dominant capillary force on their facet-to-facet contact.

  17. Dynamics of the globular cluster NGC 362

    Science.gov (United States)

    Fischer, Philippe; Welch, Douglas L.; Mateo, Mario; Cote, Patrick

    1993-01-01

    A combination of V-band CCD images and echelle spectra of member red giants is presently used to examine the internal dynamics of the globular cluster NGC 362. A total of 285 stellar spectra were obtained of 215 stars for radial velocity determinations, and the true cluster binary fraction was determined from simulations to be 0.15 for circular orbits and 0.27 for orbits with an f(e) = e (eccentricity) distribution function. An overabundance of binaries is surmised for NGC 362 on this basis.

  18. Clustering of continuous distributions of charge

    Science.gov (United States)

    Heyes, D. M.; Rickayzen, G.

    2014-05-01

    An investigation is carried out of the association and clustering of equimolar mixtures of oppositely charged Gaussian charge distributions (CDs) of the form ∼ exp ( - r2 /2α2), where r is the separation between the centres of charge and α governs the extent of charge spreading (α→0 is the point charge limit). The results of molecular dynamics (MD) and Ornstein-Zernike integral equation with the mean spherical approximation (MSA) and hypernetted-chain (HNC) closures are compared for these systems. The MD and HNC radial distribution functions, g(r), agree very well for not too small α. The MD and MSA, g(r), also agree well for α ≈ 1 and greater. The potential energy per particle for the three methods also agrees well over a wider range of α values, better than might be expected from inspection of the radial distribution functions, because the dominant contributions to U come predominantly from intermediate and long distance ranges where there is good agreement between the g(r) from the MSD and HNC closures. The nature of the association and clustering of the charges as a function of α is explored through the mean nearest neighbour distance for unlike and like species and the mean and root-mean-square force. The velocity and force autocorrelation functions are also calculated; they show increasingly oscillatory behaviour in the small α limit, originating in vibrations of a pair of CDs of opposite sign.

  19. Spatial cluster detection using dynamic programming

    Directory of Open Access Journals (Sweden)

    Sverchkov Yuriy

    2012-03-01

    Full Text Available Abstract Background The task of spatial cluster detection involves finding spatial regions where some property deviates from the norm or the expected value. In a probabilistic setting this task can be expressed as finding a region where some event is significantly more likely than usual. Spatial cluster detection is of interest in fields such as biosurveillance, mining of astronomical data, military surveillance, and analysis of fMRI images. In almost all such applications we are interested both in the question of whether a cluster exists in the data, and if it exists, we are interested in finding the most accurate characterization of the cluster. Methods We present a general dynamic programming algorithm for grid-based spatial cluster detection. The algorithm can be used for both Bayesian maximum a-posteriori (MAP estimation of the most likely spatial distribution of clusters and Bayesian model averaging over a large space of spatial cluster distributions to compute the posterior probability of an unusual spatial clustering. The algorithm is explained and evaluated in the context of a biosurveillance application, specifically the detection and identification of Influenza outbreaks based on emergency department visits. A relatively simple underlying model is constructed for the purpose of evaluating the algorithm, and the algorithm is evaluated using the model and semi-synthetic test data. Results When compared to baseline methods, tests indicate that the new algorithm can improve MAP estimates under certain conditions: the greedy algorithm we compared our method to was found to be more sensitive to smaller outbreaks, while as the size of the outbreaks increases, in terms of area affected and proportion of individuals affected, our method overtakes the greedy algorithm in spatial precision and recall. The new algorithm performs on-par with baseline methods in the task of Bayesian model averaging. Conclusions We conclude that the dynamic

  20. Acoustic Cluster Therapy: In Vitro and Ex Vivo Measurement of Activated Bubble Size Distribution and Temporal Dynamics.

    Science.gov (United States)

    Healey, Andrew John; Sontum, Per Christian; Kvåle, Svein; Eriksen, Morten; Bendiksen, Ragnar; Tornes, Audun; Østensen, Jonny

    2016-05-01

    Acoustic cluster technology (ACT) is a two-component, microparticle formulation platform being developed for ultrasound-mediated drug delivery. Sonazoid microbubbles, which have a negative surface charge, are mixed with micron-sized perfluoromethylcyclopentane droplets stabilized with a positively charged surface membrane to form microbubble/microdroplet clusters. On exposure to ultrasound, the oil undergoes a phase change to the gaseous state, generating 20- to 40-μm ACT bubbles. An acoustic transmission technique is used to measure absorption and velocity dispersion of the ACT bubbles. An inversion technique computes bubble size population with temporal resolution of seconds. Bubble populations are measured both in vitro and in vivo after activation within the cardiac chambers of a dog model, with catheter-based flow through an extracorporeal measurement flow chamber. Volume-weighted mean diameter in arterial blood after activation in the left ventricle was 22 μm, with no bubbles >44 μm in diameter. After intravenous administration, 24.4% of the oil is activated in the cardiac chambers. Copyright © 2016 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  1. Evolution of defect cluster distributions during irradiation

    International Nuclear Information System (INIS)

    Wiedersich, H.

    1991-05-01

    Defects produced by irradiation are often strongly spatially correlated. Energetic primary recoil atoms produce cascades with vacant lattice sites predominantly in the central regions, and interstitial atoms at the periphery. A fraction of the defects produced form clusters during cascade events. Because of their spatial distribution more mobile interstitial atoms than vacancies are released into the matrix following the cascade events. Populations of vacancy and interstitial clusters evolve towards quasi-steady-state distributions. As long as vacancy clusters are thermally moderately stable, i.e., at temperatures below rapid self diffusion, an excess interstitial flux persists in the matrix; as a consequence, vacancy clusters formed in cascades shrink, and interstitial clusters grow. We examine the evolution of these cluster distributions, and their effects on sink strength and radiation-enhanced diffusion, as function of dose for irradiations at moderate temperatures. At temperatures at which thermal evaporation from vacancy clusters, can be neglected, the evolution of the cluster densities is characteristic of the primary recoil spectrum, but is independent of temperature or dose rate. The sink strength, radiation-enhanced diffusion, as well as other consequences of the evolving distributions such as the imbalance of the interstitial and vacancy fluxes in the matrix, approach slowly-changing quasi-steady-state values in a fraction of one displacement per atom, although certain details of the cluster distributions, e.g., the development of large interstitial loops, require several dpa's to approach steady state values. 22 refs., 6 figs

  2. Distribution-Based Cluster Structure Selection.

    Science.gov (United States)

    Yu, Zhiwen; Zhu, Xianjun; Wong, Hau-San; You, Jane; Zhang, Jun; Han, Guoqiang

    2017-11-01

    The objective of cluster structure ensemble is to find a unified cluster structure from multiple cluster structures obtained from different datasets. Unfortunately, not all the cluster structures contribute to the unified cluster structure. This paper investigates the problem of how to select the suitable cluster structures in the ensemble which will be summarized to a more representative cluster structure. Specifically, the cluster structure is first represented by a mixture of Gaussian distributions, the parameters of which are estimated using the expectation-maximization algorithm. Then, several distribution-based distance functions are designed to evaluate the similarity between two cluster structures. Based on the similarity comparison results, we propose a new approach, which is referred to as the distribution-based cluster structure ensemble (DCSE) framework, to find the most representative unified cluster structure. We then design a new technique, the distribution-based cluster structure selection strategy (DCSSS), to select a subset of cluster structures. Finally, we propose using a distribution-based normalized hypergraph cut algorithm to generate the final result. In our experiments, a nonparametric test is adopted to evaluate the difference between DCSE and its competitors. We adopt 20 real-world datasets obtained from the University of California, Irvine and knowledge extraction based on evolutionary learning repositories, and a number of cancer gene expression profiles to evaluate the performance of the proposed methods. The experimental results show that: 1) DCSE works well on the real-world datasets and 2) DCSE based on DCSSS can further improve the performance of the algorithm.

  3. A Distributed Flocking Approach for Information Stream Clustering Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Xiaohui [ORNL; Potok, Thomas E [ORNL

    2006-01-01

    Intelligence analysts are currently overwhelmed with the amount of information streams generated everyday. There is a lack of comprehensive tool that can real-time analyze the information streams. Document clustering analysis plays an important role in improving the accuracy of information retrieval. However, most clustering technologies can only be applied for analyzing the static document collection because they normally require a large amount of computation resource and long time to get accurate result. It is very difficult to cluster a dynamic changed text information streams on an individual computer. Our early research has resulted in a dynamic reactive flock clustering algorithm which can continually refine the clustering result and quickly react to the change of document contents. This character makes the algorithm suitable for cluster analyzing dynamic changed document information, such as text information stream. Because of the decentralized character of this algorithm, a distributed approach is a very natural way to increase the clustering speed of the algorithm. In this paper, we present a distributed multi-agent flocking approach for the text information stream clustering and discuss the decentralized architectures and communication schemes for load balance and status information synchronization in this approach.

  4. The Dynamics of Overlapping Clusters

    DEFF Research Database (Denmark)

    Reckendrees, Alfred

    to a powerful industrial region. The implementation and diffusion of the factory system and the economic impact of adapted and new institutions make the core of this paper. Reciprocal interconnections between firms of different clusters shaped the region and created economic dynamics. Investments transgressed......The economic transition characterizing the process of European industrialization in the 19th century was concentrated on regions rather than on states. In the first half of the 19th century, the region of Aachen (in the west of Prussia) pioneered on the territory of the German states and developed...... the boundaries of single industries and new industries emerged. One important feature of the regional production system was cross-sectional knowledge transfer; a second was institutions supportive to this process....

  5. The Dynamics of Overlapping Clusters

    DEFF Research Database (Denmark)

    Reckendrees, Alfred

    The economic transition characterizing the process of European industrialization in the 19th century was concentrated on regions rather than on states. In the first half of the 19th century, the region of Aachen (in the west of Prussia) pioneered on the territory of the German states and developed...... to a powerful industrial region. The implementation and diffusion of the factory system and the economic impact of adapted and new institutions make the core of this paper. Reciprocal interconnections between firms of different clusters shaped the region and created economic dynamics. Investments transgressed...... the boundaries of single industries and new industries emerged. One important feature of the regional production system was cross-sectional knowledge transfer; a second was institutions supportive to this process....

  6. Cluster analysis for determining distribution center location

    Science.gov (United States)

    Lestari Widaningrum, Dyah; Andika, Aditya; Murphiyanto, Richard Dimas Julian

    2017-12-01

    Determination of distribution facilities is highly important to survive in the high level of competition in today’s business world. Companies can operate multiple distribution centers to mitigate supply chain risk. Thus, new problems arise, namely how many and where the facilities should be provided. This study examines a fast-food restaurant brand, which located in the Greater Jakarta. This brand is included in the category of top 5 fast food restaurant chain based on retail sales. There were three stages in this study, compiling spatial data, cluster analysis, and network analysis. Cluster analysis results are used to consider the location of the additional distribution center. Network analysis results show a more efficient process referring to a shorter distance to the distribution process.

  7. Modified Newtonian dynamics and the Coma cluster

    International Nuclear Information System (INIS)

    The, L.S.; White, S.D.M.

    1988-01-01

    The consistency of Milgrom's theory of modified Newtonian dynamics is checked against optical and X-ray data for the Coma cluster of galaxies. It is found that viable models for the cluster containing no dark matter can be constructed. They require an extensive gaseous atmosphere through which galaxies move on near-radial orbits. The gas temperature is predicted to have a shallow minimum near the cluster center; this structure may conflict with the best X-ray spectra of the cluster. 18 references

  8. Distributed controller clustering in software defined networks.

    Directory of Open Access Journals (Sweden)

    Ahmed Abdelaziz

    Full Text Available Software Defined Networking (SDN is an emerging promising paradigm for network management because of its centralized network intelligence. However, the centralized control architecture of the software-defined networks (SDNs brings novel challenges of reliability, scalability, fault tolerance and interoperability. In this paper, we proposed a novel clustered distributed controller architecture in the real setting of SDNs. The distributed cluster implementation comprises of multiple popular SDN controllers. The proposed mechanism is evaluated using a real world network topology running on top of an emulated SDN environment. The result shows that the proposed distributed controller clustering mechanism is able to significantly reduce the average latency from 8.1% to 1.6%, the packet loss from 5.22% to 4.15%, compared to distributed controller without clustering running on HP Virtual Application Network (VAN SDN and Open Network Operating System (ONOS controllers respectively. Moreover, proposed method also shows reasonable CPU utilization results. Furthermore, the proposed mechanism makes possible to handle unexpected load fluctuations while maintaining a continuous network operation, even when there is a controller failure. The paper is a potential contribution stepping towards addressing the issues of reliability, scalability, fault tolerance, and inter-operability.

  9. Distributed controller clustering in software defined networks

    Science.gov (United States)

    Gani, Abdullah; Akhunzada, Adnan; Talebian, Hamid; Choo, Kim-Kwang Raymond

    2017-01-01

    Software Defined Networking (SDN) is an emerging promising paradigm for network management because of its centralized network intelligence. However, the centralized control architecture of the software-defined networks (SDNs) brings novel challenges of reliability, scalability, fault tolerance and interoperability. In this paper, we proposed a novel clustered distributed controller architecture in the real setting of SDNs. The distributed cluster implementation comprises of multiple popular SDN controllers. The proposed mechanism is evaluated using a real world network topology running on top of an emulated SDN environment. The result shows that the proposed distributed controller clustering mechanism is able to significantly reduce the average latency from 8.1% to 1.6%, the packet loss from 5.22% to 4.15%, compared to distributed controller without clustering running on HP Virtual Application Network (VAN) SDN and Open Network Operating System (ONOS) controllers respectively. Moreover, proposed method also shows reasonable CPU utilization results. Furthermore, the proposed mechanism makes possible to handle unexpected load fluctuations while maintaining a continuous network operation, even when there is a controller failure. The paper is a potential contribution stepping towards addressing the issues of reliability, scalability, fault tolerance, and inter-operability. PMID:28384312

  10. CLUSTER DYNAMICS LARGELY SHAPES PROTOPLANETARY DISK SIZES

    Energy Technology Data Exchange (ETDEWEB)

    Vincke, Kirsten; Pfalzner, Susanne, E-mail: kvincke@mpifr-bonn.mpg.de [Max Planck Institute for Radio Astronomy, Auf dem Hügel 69, D-53121 Bonn (Germany)

    2016-09-01

    To what degree the cluster environment influences the sizes of protoplanetary disks surrounding young stars is still an open question. This is particularly true for the short-lived clusters typical for the solar neighborhood, in which the stellar density and therefore the influence of the cluster environment change considerably over the first 10 Myr. In previous studies, the effect of the gas on the cluster dynamics has often been neglected; this is remedied here. Using the code NBody6++, we study the stellar dynamics in different developmental phases—embedded, expulsion, and expansion—including the gas, and quantify the effect of fly-bys on the disk size. We concentrate on massive clusters (M {sub cl} ≥ 10{sup 3}–6 ∗ 10{sup 4} M {sub Sun}), which are representative for clusters like the Orion Nebula Cluster (ONC) or NGC 6611. We find that not only the stellar density but also the duration of the embedded phase matters. The densest clusters react fastest to the gas expulsion and drop quickly in density, here 98% of relevant encounters happen before gas expulsion. By contrast, disks in sparser clusters are initially less affected, but because these clusters expand more slowly, 13% of disks are truncated after gas expulsion. For ONC-like clusters, we find that disks larger than 500 au are usually affected by the environment, which corresponds to the observation that 200 au-sized disks are common. For NGC 6611-like clusters, disk sizes are cut-down on average to roughly 100 au. A testable hypothesis would be that the disks in the center of NGC 6611 should be on average ≈20 au and therefore considerably smaller than those in the ONC.

  11. Dynamics of Galaxy Clusters and their Outskirts

    DEFF Research Database (Denmark)

    Falco, Martina

    Galaxy clusters have demonstrated to be powerful probes of cosmology, since their mass and abundance depend on the cosmological model that describes the Universe and on the gravitational formation process of cosmological structures. The main challenge in using clusters to constrain cosmology...... is that their masses cannot be measured directly, but need to be inferred indirectly through their observable properties. The most common methods extract the cluster mass from their strong X-ray emission or from the measured redshifts of the galaxy members. The gravitational lensing effect caused by clusters...... on the background galaxies is also an important trace of their total mass distribution.In the work presented within this thesis, we exploit the connection between the gravitational potential of galaxy clusters and the kinematical properties of their surroundings, in order to determine the total cluster mass...

  12. Dynamic Cities and Creative Clusters

    OpenAIRE

    Wu, Weiping

    2005-01-01

    The author focuses on how urban policies and the clustering of creative industries has influenced urban outcomes. The set of creative industries include those with output protectable under some form of intellectual property law. More specifically, this sub-sector encompasses software, multimedia, video games, industrial design, fashion, publishing, and research and development. The cities that form the basis for the empirical investigations are those where policy-induced transitions have been...

  13. Mass distribution of products of cluster impacts

    International Nuclear Information System (INIS)

    Beuhler, R.J.; Friedman, L.

    1988-01-01

    Mass distributions of ionic atomic and molecular fragments sputtered from carbon surfaces by singly charged positive cluster ions containing 80 water molecules have been determined. With cluster kinetic energy of 240 keV significant yields of molecular fragments containing up to 21 carbon atoms were observed. Ion yields were used to estimate relative yields of neutral fragments with the assumption that relative yields of the respective ionic and neutral sputtering processes were determined by kinetic factors which could be evaluated independently. The derived neutral yields were then used to estimate the fraction of total projectile energy utilized in evaporative cooling, i.e., sputtering. The results indicate a major fraction of the energy available is used in the cluster sputtering process. 9 refs., 1 tab

  14. Cardiac mitochondria exhibit dynamic functional clustering

    Directory of Open Access Journals (Sweden)

    Felix Tobias Kurz

    2014-09-01

    Full Text Available Multi-oscillatory behavior of mitochondrial inner membrane potential ΔΨm in self-organized cardiac mitochondrial networks can be triggered by metabolic or oxidative stress. Spatio-temporal analyses of cardiac mitochondrial networks have shown that mitochondria are heterogeneously organized in synchronously oscillating clusters in which the mean cluster frequency and size are inversely correlated, thus suggesting a modulation of cluster frequency through local inter-mitochondrial coupling. In this study, we propose a method to examine the mitochondrial network's topology through quantification of its dynamic local clustering coefficients. Individual mitochondrial ΔΨm oscillation signals were identified for each cardiac myocyte and cross-correlated with all network mitochondria using previously described methods (Kurz et al., 2010. Time-varying inter-mitochondrial connectivity, defined for mitochondria in the whole network whose signals are at least 90% correlated at any given time point, allowed considering functional local clustering coefficients. It is shown that mitochondrial clustering in isolated cardiac myocytes changes dynamically and is significantly higher than for random mitochondrial networks that are constructed using the Erdös-Rényi model based on the same sets of vertices. The network's time-averaged clustering coefficient for cardiac myocytes was found to be 0.500 ± 0.051 (N=9 versus 0.061 ± 0.020 for random networks, respectively. Our results demonstrate that cardiac mitochondria constitute a network with dynamically connected constituents whose topological organization is prone to clustering. Cluster partitioning in networks of coupled oscillators has been observed in scale-free and chaotic systems and is therefore in good agreement with previous models of cardiac mitochondrial networks (Aon et al., 2008.

  15. Distributed MDSplus database performance with Linux clusters

    International Nuclear Information System (INIS)

    Minor, D.H.; Burruss, J.R.

    2006-01-01

    The staff at the DIII-D National Fusion Facility, operated for the USDOE by General Atomics, are investigating the use of grid computing and Linux technology to improve performance in our core data management services. We are in the process of converting much of our functionality to cluster-based and grid-enabled software. One of the most important pieces is a new distributed version of the MDSplus scientific data management system that is presently used to support fusion research in over 30 countries worldwide. To improve data handling performance, the staff is investigating the use of Linux clusters for both data clients and servers. The new distributed capability will result in better load balancing between these clients and servers, and more efficient use of network resources resulting in improved support of the data analysis needs of the scientific staff

  16. Cluster dynamics transcending chemical dynamics toward nuclear fusion.

    Science.gov (United States)

    Heidenreich, Andreas; Jortner, Joshua; Last, Isidore

    2006-07-11

    Ultrafast cluster dynamics encompasses femtosecond nuclear dynamics, attosecond electron dynamics, and electron-nuclear dynamics in ultraintense laser fields (peak intensities 10(15)-10(20) W.cm(-2)). Extreme cluster multielectron ionization produces highly charged cluster ions, e.g., (C(4+)(D(+))(4))(n) and (D(+)I(22+))(n) at I(M) = 10(18) W.cm(-2), that undergo Coulomb explosion (CE) with the production of high-energy (5 keV to 1 MeV) ions, which can trigger nuclear reactions in an assembly of exploding clusters. The laser intensity and the cluster size dependence of the dynamics and energetics of CE of (D(2))(n), (HT)(n), (CD(4))(n), (DI)(n), (CD(3)I)(n), and (CH(3)I)(n) clusters were explored by electrostatic models and molecular dynamics simulations, quantifying energetic driving effects, and kinematic run-over effects. The optimization of table-top dd nuclear fusion driven by CE of deuterium containing heteroclusters is realized for light-heavy heteroclusters of the largest size, which allows for the prevalence of cluster vertical ionization at the highest intensity of the laser field. We demonstrate a 7-orders-of-magnitude enhancement of the yield of dd nuclear fusion driven by CE of light-heavy heteroclusters as compared with (D(2))(n) clusters of the same size. Prospective applications for the attainment of table-top nucleosynthesis reactions, e.g., (12)C(P,gamma)(13)N driven by CE of (CH(3)I)(n) clusters, were explored.

  17. A dynamical condition for a relativistic galaxy cluster model

    International Nuclear Information System (INIS)

    Trevese, D.; Vignato, A.

    1976-01-01

    In an attempt to give a coherent interpretation of the secondary maximum in the density distribution of clusters an approximate metric tensor proposed by other authors is used with the purpose of building a relativistic generalization of the isothermal models of galaxy clusters. Although such a generalization gives rise to oscillations in the density distribution, the quantitative agreement with the observational data is unsatisfactory. The analysis of the metric tensor used brings out the points (i) the approximation on which the metric is based is not suitable for describing an actual galaxy and (ii) the dynamical conditions of clusters require inclusion of a cosmological expansion, and of anisotropic distribution function in the phase-space. (Auth.)

  18. Nonuniform Sparse Data Clustering Cascade Algorithm Based on Dynamic Cumulative Entropy

    Directory of Open Access Journals (Sweden)

    Ning Li

    2016-01-01

    Full Text Available A small amount of prior knowledge and randomly chosen initial cluster centers have a direct impact on the accuracy of the performance of iterative clustering algorithm. In this paper we propose a new algorithm to compute initial cluster centers for k-means clustering and the best number of the clusters with little prior knowledge and optimize clustering result. It constructs the Euclidean distance control factor based on aggregation density sparse degree to select the initial cluster center of nonuniform sparse data and obtains initial data clusters by multidimensional diffusion density distribution. Multiobjective clustering approach based on dynamic cumulative entropy is adopted to optimize the initial data clusters and the best number of the clusters. The experimental results show that the newly proposed algorithm has good performance to obtain the initial cluster centers for the k-means algorithm and it effectively improves the clustering accuracy of nonuniform sparse data by about 5%.

  19. Dynamical processes in space: Cluster results

    Directory of Open Access Journals (Sweden)

    C. P. Escoubet

    2013-06-01

    Full Text Available After 12 years of operations, the Cluster mission continues to successfully fulfil its scientific objectives. The main goal of the Cluster mission, comprised of four identical spacecraft, is to study in three dimensions small-scale plasma structures in key plasma regions of the Earth's environment: solar wind and bow shock, magnetopause, polar cusps, magnetotail, plasmasphere and auroral zone. During the course of the mission, the relative distance between the four spacecraft has been varied from 20 km to 36 000 km to study the scientific regions of interest at different scales. Since summer 2005, new multi-scale constellations have been implemented, wherein three spacecraft (C1, C2, C3 are separated by 10 000 km, while the fourth one (C4 is at a variable distance ranging between 20 km and 10 000 km from C3. Recent observations were conducted in the auroral acceleration region with the spacecraft separated by 1000s km. We present highlights of the results obtained during the last 12 years on collisionless shocks, magnetopause waves, magnetotail dynamics, plasmaspheric structures, and the auroral acceleration region. In addition, we highlight Cluster results on understanding the impact of Coronal Mass Ejections (CME on the Earth environment. We will also present Cluster data accessibility through the Cluster Science Data System (CSDS, and the Cluster Active Archive (CAA, which was implemented to provide a permanent and public archive of high resolution Cluster data from all instruments.

  20. Electrostatic effects on clustering and ion dynamics in ionomer melts

    Science.gov (United States)

    Ma, Boran; Nguyen, Trung; Pryamitsyn, Victor; Olvera de La Cruz, Monica

    An understanding of the relationships between ionomer chain morphology, dynamics and counter-ion mobility is a key factor in the design of ion conducting membranes for battery applications. In this study, we investigate the influence of electrostatic coupling between randomly charged copolymers (ionomers) and counter ions on the structural and dynamic features of a model system of ionomer melts. Using coarse-grained molecular dynamics (CGMD) simulations, we found that variations in electrostatic coupling strength (Γ) remarkably affect the formation of ion-counter ion clusters, ion mobility, and polymer dynamics for a range of charged monomer fractions. Specifically, an increase in Γ leads to larger ionic cluster sizes and reduced polymer and ion mobility. Analysis of the distribution of the radius of gyration of the clusters further reveals that the fractal dimension of the ion clusters is nearly independent from Γ for all the cases studied. Finally, at sufficiently high values of Γ, we observed arrested heterogeneous ions mobility, which is correlated with an increase in ion cluster size. These findings provide insight into the role of electrostatics in governing the nanostructures formed by ionomers.

  1. Negative binomial multiplicity distribution from binomial cluster production

    International Nuclear Information System (INIS)

    Iso, C.; Mori, K.

    1990-01-01

    Two-step interpretation of negative binomial multiplicity distribution as a compound of binomial cluster production and negative binomial like cluster decay distribution is proposed. In this model we can expect the average multiplicity for the cluster production increases with increasing energy, different from a compound Poisson-Logarithmic distribution. (orig.)

  2. Dynamical evolution of the Orion nebula cluster

    Science.gov (United States)

    Scally, Aylwyn; Clarke, Cathie; McCaughrean, Mark J.

    2005-04-01

    Observations of star formation in the Galaxy support the conclusion that most stars - including our own - form in an environment like the Orion nebula cluster (ONC). We construct a range of dynamical models of the ONC, using Aarseth's NBODY6 code, and explore their consequences for the origins of the cluster and its subsequent evolution. We find that the most acceptable fits to the cluster density profile are obtained in models where the cluster is set up in virial equilibrium and where the cluster extends well outside the limits of existing photometric surveys. However, current estimates of the virial ratio suggest the cluster is already unbound. We show that the size and age of the ONC in this case imply either that it became unbound only very recently, or else that it has expanded quasi-statically. In the latter case, its initial central density may have exceeded its current value by 1-2 orders of magnitude. We stress the importance of future proper motion experiments to distinguish between these possibilities.

  3. Large amplitude femtosecond electron dynamics in metal clusters

    CERN Document Server

    Daligault, J

    2003-01-01

    We present a theoretical model that allows us to study linear and non-linear aspects of the femtosecond electron dynamics in metal clusters. The theoretical approach consists in the classical limit of the time-dependent Kohn-Sham equations. The electrons are described by a phase-space distribution function which satisfies a Vlasov-like equation while the ions are treated classically. This allows simulations for clusters containing several hundreds of atoms and extending up to several hundreds of femtoseconds during which the description conserves the fermionic character of the electron distribution. This semi-quantal approach compares very well with the purely quantal treatment. As an application of this approach, we show the prominent role of the electron dynamics during and after the interaction with an intense femtosecond laser pulse.

  4. Investigation of Melting Dynamics of Hafnium Clusters.

    Science.gov (United States)

    Ng, Wei Chun; Lim, Thong Leng; Yoon, Tiem Leong

    2017-03-27

    Melting dynamics of hafnium clusters are investigated using a novel approach based on the idea of the chemical similarity index. Ground state configurations of small hafnium clusters are first derived using Basin-Hopping and Genetic Algorithm in the parallel tempering mode, employing the COMB potential in the energy calculator. These assumed ground state structures are verified by using the Low Lying Structures (LLS) method. The melting process is carried out either by using the direct heating method or prolonged simulated annealing. The melting point is identified by a caloric curve. However, it is found that the global similarity index is much more superior in locating premelting and total melting points of hafnium clusters.

  5. Dynamics of Planetary Systems in Star Clusters

    Science.gov (United States)

    Spurzem, R.; Giersz, M.; Heggie, D. C.; Lin, D. N. C.

    2009-05-01

    At least 10%-15% of nearby Sunlike stars have known Jupiter-mass planets. In contrast, very few planets are found in mature open and globular clusters such as the Hyades and 47 Tuc. We explore here the possibility that this dichotomy is due to the postformation disruption of planetary systems associated with the stellar encounters in long-lived clusters. One supporting piece of evidence for this scenario is the discovery of freely floating low-mass objects in star forming regions. We use two independent numerical approaches, a hybrid Monte Carlo and a direct N-body method, to simulate the impact of the encounters. We show that the results of numerical simulations are in reasonable agreement with analytical determinations in the adiabatic and impulsive limits. They indicate that distant stellar encounters generally do not significantly modify the compact and nearly circular orbits. However, moderately close stellar encounters, which are likely to occur in dense clusters, can excite planets' orbital eccentricity and induce dynamical instability in systems that are closely packed with multiple planets. The disruption of planetary systems occurs primarily through occasional nearly parabolic, nonadiabatic encounters, though eccentricity of the planets evolves through repeated hyperbolic adiabatic encounters that accumulate small-amplitude changes. The detached planets are generally retained by the potential of their host clusters as free floaters in young stellar clusters such as σ Orionis. We compute effective cross sections for the dissolution of planetary systems and show that, for all initial eccentricities, dissolution occurs on timescales that are longer than the dispersion of small stellar associations, but shorter than the age of typical open and globular clusters. Although it is much more difficult to disrupt short-period planets, close encounters can excite modest eccentricity among them, such that subsequent tidal dissipation leads to orbital decay, tidal

  6. The distribution of clusters in the southern ACO catalog

    International Nuclear Information System (INIS)

    Batuski, D.J.; Bahcall, N.A.; Olowin, R.P.; Burns, J.O.

    1989-01-01

    The distribution of rich clusters of galaxies in the new southern catalog of Abell, Corwin, and Olowin (ACO, 1989) is examined. A comparison with the cluster distribution in the northern Abell catalog, published in 1958, is presented. The similarities as well as the differences between the catalogs are highlighted. The angular cluster correlation function of the ACO catalog is consistent with the Abell cluster correlation, showing strong superclustering to about 50/h Mpc. The correlation amplitude scales with depth, as expected for real spatial clustering. Plate-to-plate variation effects are investigated; no significant impact of the latter on the cluster correlation is observed. 19 refs

  7. Cluster analysis of word frequency dynamics

    Science.gov (United States)

    Maslennikova, Yu S.; Bochkarev, V. V.; Belashova, I. A.

    2015-01-01

    This paper describes the analysis and modelling of word usage frequency time series. During one of previous studies, an assumption was put forward that all word usage frequencies have uniform dynamics approaching the shape of a Gaussian function. This assumption can be checked using the frequency dictionaries of the Google Books Ngram database. This database includes 5.2 million books published between 1500 and 2008. The corpus contains over 500 billion words in American English, British English, French, German, Spanish, Russian, Hebrew, and Chinese. We clustered time series of word usage frequencies using a Kohonen neural network. The similarity between input vectors was estimated using several algorithms. As a result of the neural network training procedure, more than ten different forms of time series were found. They describe the dynamics of word usage frequencies from birth to death of individual words. Different groups of word forms were found to have different dynamics of word usage frequency variations.

  8. Cluster analysis of word frequency dynamics

    International Nuclear Information System (INIS)

    Maslennikova, Yu S; Bochkarev, V V; Belashova, I A

    2015-01-01

    This paper describes the analysis and modelling of word usage frequency time series. During one of previous studies, an assumption was put forward that all word usage frequencies have uniform dynamics approaching the shape of a Gaussian function. This assumption can be checked using the frequency dictionaries of the Google Books Ngram database. This database includes 5.2 million books published between 1500 and 2008. The corpus contains over 500 billion words in American English, British English, French, German, Spanish, Russian, Hebrew, and Chinese. We clustered time series of word usage frequencies using a Kohonen neural network. The similarity between input vectors was estimated using several algorithms. As a result of the neural network training procedure, more than ten different forms of time series were found. They describe the dynamics of word usage frequencies from birth to death of individual words. Different groups of word forms were found to have different dynamics of word usage frequency variations

  9. Cluster Dynamics: Laying the Foundation for Tailoring the Design of Cluster ASSE

    Science.gov (United States)

    2016-02-25

    AFRL-AFOSR-VA-TR-2016-0081 CLUSTER DYNAMICS: LAYING THE FOUNDATION FOR TAILORING THE DESIGN OF CLUSTER ASSE Albert Castleman PENNSYLVANIA STATE...15-10-2015 4. TITLE AND SUBTITLE CLUSTER DYNAMICS: LAYING THE FOUNDATION FOR TAILORING THE DESIGN OF CLUSTER ASSEMBLED NANOSCALE MATERIALS 5a... clusters as the building blocks of new materials with tailored properties that are beneficial to the AFOSR. Our continuing program is composed of two

  10. Changes in tropical precipitation cluster size distributions under global warming

    Science.gov (United States)

    Neelin, J. D.; Quinn, K. M.

    2016-12-01

    The total amount of precipitation integrated across a tropical storm or other precipitation feature (contiguous clusters of precipitation exceeding a minimum rain rate) is a useful measure of the aggregate size of the disturbance. To establish baseline behavior in current climate, the probability distribution of cluster sizes from multiple satellite retrievals and National Center for Environmental Prediction (NCEP) reanalysis is compared to those from Coupled Model Intercomparison Project (CMIP5) models and the Geophysical Fluid Dynamics Laboratory high-resolution atmospheric model (HIRAM-360 and -180). With the caveat that a minimum rain rate threshold is important in the models (which tend to overproduce low rain rates), the models agree well with observations in leading properties. In particular, scale-free power law ranges in which the probability drops slowly with increasing cluster size are well modeled, followed by a rapid drop in probability of the largest clusters above a cutoff scale. Under the RCP 8.5 global warming scenario, the models indicate substantial increases in probability (up to an order of magnitude) of the largest clusters by the end of century. For models with continuous time series of high resolution output, there is substantial spread on when these probability increases for the largest precipitation clusters should be detectable, ranging from detectable within the observational period to statistically significant trends emerging only in the second half of the century. Examination of NCEP reanalysis and SSMI/SSMIS series of satellite retrievals from 1979 to present does not yield reliable evidence of trends at this time. The results suggest improvements in inter-satellite calibration of the SSMI/SSMIS retrievals could aid future detection.

  11. Enforcing Resource Sharing Agreements Among Distributed Server Clusters

    National Research Council Canada - National Science Library

    Zhao, Tao; Karamcheti, Vijay

    2001-01-01

    Future scalable, high throughput, and high performance applications are likely to execute on platforms constructed by clustering multiple autonomous distributed servers, with resource access governed...

  12. Analyzing Big Data with Dynamic Quantum Clustering

    OpenAIRE

    Weinstein, M.; Meirer, F.; Hume, A.; Sciau, Ph.; Shaked, G.; Hofstetter, R.; Persi, E.; Mehta, A.; Horn, D.

    2013-01-01

    How does one search for a needle in a multi-dimensional haystack without knowing what a needle is and without knowing if there is one in the haystack? This kind of problem requires a paradigm shift - away from hypothesis driven searches of the data - towards a methodology that lets the data speak for itself. Dynamic Quantum Clustering (DQC) is such a methodology. DQC is a powerful visual method that works with big, high-dimensional data. It exploits variations of the density of the data (in f...

  13. Single-cluster dynamics for the random-cluster model

    NARCIS (Netherlands)

    Deng, Y.; Qian, X.; Blöte, H.W.J.

    2009-01-01

    We formulate a single-cluster Monte Carlo algorithm for the simulation of the random-cluster model. This algorithm is a generalization of the Wolff single-cluster method for the q-state Potts model to noninteger values q>1. Its results for static quantities are in a satisfactory agreement with those

  14. Mass and velocity distributions of low energy cluster beams

    Energy Technology Data Exchange (ETDEWEB)

    Compagnini, Giuseppe [Dipartimento di Scienze Chimiche Universita di Catania and MATIS-INFM, Viale A. Doria 6 Catania 95125 (Italy)]. E-mail: gcompagnini@unict.it; D' Urso, Luisa [Dipartimento di Scienze Chimiche Universita di Catania and MATIS-INFM, Viale A. Doria 6 Catania 95125 (Italy); Puglisi, Orazio [Dipartimento di Scienze Chimiche Universita di Catania and MATIS-INFM, Viale A. Doria 6 Catania 95125 (Italy)

    2006-07-15

    We have recently generated several low energy cluster beams by using a laser vaporization source and a pulsed He stream. This has been done both for covalent (silicon and carbon) and metallic (gold) materials. In this work we present a simple procedure to carefully measure the speed and speed distribution of the obtained clusters with the help of an orthogonal time of flight mass spectrometer. Results show average speed values in the range 700-1000 m/s with a mild variation by changing the gas backing pressure and the cluster mass inside each cluster train. Detailed speed distributions for each cluster's mass will be given.

  15. Dynamic parallel ROOT facility clusters on the Alice Environment

    International Nuclear Information System (INIS)

    Luzzi, C; Betev, L; Carminati, F; Grigoras, C; Saiz, P; Manafov, A

    2012-01-01

    The ALICE collaboration has developed a production environment (AliEn) that implements the full set of the Grid tools enabling the full offline computational work-flow of the experiment, simulation, reconstruction and data analysis, in a distributed and heterogeneous computing environment. In addition to the analysis on the Grid, ALICE uses a set of local interactive analysis facilities installed with the Parallel ROOT Facility (PROOF). PROOF enables physicists to analyze medium-sized (order of 200-300 TB) data sets on a short time scale. The default installation of PROOF is on a static dedicated cluster, typically 200-300 cores. This well-proven approach, has its limitations, more specifically for analysis of larger datasets or when the installation of a dedicated cluster is not possible. Using a new framework called PoD (Proof on Demand), PROOF can be used directly on Grid-enabled clusters, by dynamically assigning interactive nodes on user request. The integration of Proof on Demand in the AliEn framework provides private dynamic PROOF clusters as a Grid service. This functionality is transparent to the user who will submit interactive jobs to the AliEn system.

  16. ClusterControl: a web interface for distributing and monitoring bioinformatics applications on a Linux cluster.

    Science.gov (United States)

    Stocker, Gernot; Rieder, Dietmar; Trajanoski, Zlatko

    2004-03-22

    ClusterControl is a web interface to simplify distributing and monitoring bioinformatics applications on Linux cluster systems. We have developed a modular concept that enables integration of command line oriented program into the application framework of ClusterControl. The systems facilitate integration of different applications accessed through one interface and executed on a distributed cluster system. The package is based on freely available technologies like Apache as web server, PHP as server-side scripting language and OpenPBS as queuing system and is available free of charge for academic and non-profit institutions. http://genome.tugraz.at/Software/ClusterControl

  17. Binary cluster collision dynamics and minimum energy conformations

    Energy Technology Data Exchange (ETDEWEB)

    Muñoz, Francisco [Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle (Germany); Departamento de Física, Facultad de Ciencias, Universidad de Chile, Santiago (Chile); Centro para el Desarrollo de la Nanociencia y Nanotecnología, CEDENNA, Avenida Ecuador 3493, Santiago (Chile); Rogan, José; Valdivia, J.A. [Departamento de Física, Facultad de Ciencias, Universidad de Chile, Santiago (Chile); Centro para el Desarrollo de la Nanociencia y Nanotecnología, CEDENNA, Avenida Ecuador 3493, Santiago (Chile); Varas, A. [Departamento de Física, Facultad de Ciencias, Universidad de Chile, Santiago (Chile); Nano-Bio Spectroscopy Group, ETSF Scientific Development Centre, Departamento de Física de Materiales, Universidad del País Vasco UPV/EHU, Av. Tolosa 72, E-20018 San Sebastián (Spain); Kiwi, Miguel, E-mail: m.kiwi.t@gmail.com [Departamento de Física, Facultad de Ciencias, Universidad de Chile, Santiago (Chile); Centro para el Desarrollo de la Nanociencia y Nanotecnología, CEDENNA, Avenida Ecuador 3493, Santiago (Chile)

    2013-10-15

    The collision dynamics of one Ag or Cu atom impinging on a Au{sub 12} cluster is investigated by means of DFT molecular dynamics. Our results show that the experimentally confirmed 2D to 3D transition of Au{sub 12}→Au{sub 13} is mostly preserved by the resulting planar Au{sub 12}Ag and Au{sub 12}Cu minimum energy clusters, which is quite remarkable in view of the excess energy, well larger than the 2D–3D potential barrier height. The process is accompanied by a large s−d hybridization and charge transfer from Au to Ag or Cu. The dynamics of the collision process mainly yields fusion of projectile and target, however scattering and cluster fragmentation also occur for large energies and large impact parameters. While Ag projectiles favor fragmentation, Cu favors scattering due to its smaller mass. The projectile size does not play a major role in favoring the fragmentation or scattering channels. By comparing our collision results with those obtained by an unbiased minimum energy search of 4483 Au{sub 12}Ag and 4483 Au{sub 12}Cu configurations obtained phenomenologically, we find that there is an extra bonus: without increase of computer time collisions yield the planar lower energy structures that are not feasible to obtain using semi-classical potentials. In fact, we conclude that phenomenological potentials do not even provide adequate seeds for the search of global energy minima for planar structures. Since the fabrication of nanoclusters is mainly achieved by synthesis or laser ablation, the set of local minima configurations we provide here, and their distribution as a function of energy, are more relevant than the global minimum to analyze experimental results obtained at finite temperatures, and is consistent with the dynamical coexistence of 2D and 3D liquid Au clusters conformations obtained previously.

  18. Spatial distribution of ion charges in fast, partially stripped clusters traversing solid targets

    CERN Document Server

    Miskovic, Z L; Goodman, F O; Wang, Y N

    2002-01-01

    Joint statistical description of the distribution of ion charge states and the spatial structure of a cluster, made of heavy ions, allows a self-consistent generalization of the Brandt-Kitagawa variational theory, including dynamically-screened inter-ionic interactions, in a form of a non-linear integral equation. Solution of such an equation for fast clusters passing very thin foils shows the familiar reduction of charge per ion, compared to the charge on an isotactic ion, which is rather non-homogeneously distributed throughout the volume of the cluster. As a consequence, the distribution of individual ion charges in the cluster exhibits large dispersion around an average value, which drops with the increasing cluster size.

  19. Holes in the distribution of rich clusters of galaxies

    International Nuclear Information System (INIS)

    Burns, J.O.

    1988-01-01

    The properties of voids in the distribution of Abell clusters of galaxies are described. Cluster voids, such as that in Bootes, serve as markers of large candidate voids of galaxies. The advantages and disadvantages of using rich clusters as tracers of large-scale structures are reviewed. One new 40/h Mpc diameter void of galaxies and clusters in Pisces-Cetus is described in detail. It is found that numerical simulations of models with Gaussian initial conditions do not reproduce the void or filament structures observed within the Abell cluster catalog. The implications of this discrepancy for future observations and models are discussed. 26 references

  20. Vegetation patchiness: Pareto statistics, cluster dynamics and desertification.

    Science.gov (United States)

    Shnerb, N. M.

    2009-04-01

    Recent studies [1-4] of cluster distribution of vegetation in the dryland revealed Pareto statistics for the size of spatial colonies. These results were supported by cellular automata simulations that yield robust criticality for endogenous pattern formation based on positive feedback. We show that this self-organized criticality is a manifestation of the law of proportion effec: mapping the stochastic model to a Markov birth-death process, the transition rates are shown to scale linearly with cluster size. This mapping provides a connection between patch statistics and the dynamics of the ecosystem; the "first passage time" for different colonies emerges as a powerful tool that discriminates between endogenous and exogenous clustering mechanisms. Imminent catastrophic shifts (like desertification) manifest themselves in a drastic change of the stability properties of spatial colonies, as the chance of a cluster to disappear depends logarithmically, rather than linearly, on its size. [1] Scanlon et. al., Nature 449, 209212 [2007]. [2] Kefi et. al., Nature 449, 213217 [2007]. [3] Sole R., Nature 449, p. 151 [2007]. [4] Vandermeer et. al., Nature 451, p. 457 [2008].

  1. Distributed Dynamic Condition Response Structures

    DEFF Research Database (Denmark)

    Hildebrandt, Thomas; Mukkamala, Raghava Rao

    We present distributed dynamic condition response structures as a declarative process model inspired by the workflow language employed by our industrial partner and conservatively generalizing labelled event structures. The model adds to event structures the possibility to 1) finitely specify...... repeated, possibly infinite behavior, 2) finitely specify fine-grained acceptance conditions for (possibly infinite) runs based on the notion of responses and 3) distribute events via roles. We give a graphical notation inspired by related work by van der Aalst et al and formalize the execution semantics...... as a labelled transition system. Exploration of the relationship between dynamic condition response structures and traditional models for concurrency, application to more complex scenarios, and further extensions of the model is left to future work....

  2. Oscillator clustering in a resource distribution chain

    DEFF Research Database (Denmark)

    Postnov, D.; Sosnovtseva, Olga; Mosekilde, Erik

    2005-01-01

    The paper investigates the special clustering phenomena that one can observe in systems of nonlinear oscillators that are coupled via a shared flow of primary resources (or a common power supply). This type of coupling, which appears to be quite frequent in nature, implies that one can no longer...

  3. Dynamic Characteristics Analysis and Stabilization of PV-Based Multiple Microgrid Clusters

    DEFF Research Database (Denmark)

    Zhao, Zhuoli; Yang, Ping; Wang, Yuewu

    2018-01-01

    As the penetration of PV generation increases, there is a growing operational demand on PV systems to participate in microgrid frequency regulation. It is expected that future distribution systems will consist of multiple microgrid clusters. However, interconnecting PV microgrids may lead to system...... interactions and instability. To date, no research work has been done to analyze the dynamic behavior and enhance the stability of microgrid clusters considering the dynamics of the PV primary sources and dc links. To fill this gap, this paper presents comprehensive modeling, analysis, and stabilization of PV......-based multiple microgrid clusters. A detailed small-signal model for PV-based microgrid clusters considering local adaptive dynamic droop control mechanism of the voltage-source PV system is developed. The complete dynamic model is then used to access and compare the dynamic characteristics of the single...

  4. Moving Target Tracking through Distributed Clustering in Directional Sensor Networks

    Directory of Open Access Journals (Sweden)

    Asma Enayet

    2014-12-01

    Full Text Available The problem of moving target tracking in directional sensor networks (DSNs introduces new research challenges, including optimal selection of sensing and communication sectors of the directional sensor nodes, determination of the precise location of the target and an energy-efficient data collection mechanism. Existing solutions allow individual sensor nodes to detect the target’s location through collaboration among neighboring nodes, where most of the sensors are activated and communicate with the sink. Therefore, they incur much overhead, loss of energy and reduced target tracking accuracy. In this paper, we have proposed a clustering algorithm, where distributed cluster heads coordinate their member nodes in optimizing the active sensing and communication directions of the nodes, precisely determining the target location by aggregating reported sensing data from multiple nodes and transferring the resultant location information to the sink. Thus, the proposed target tracking mechanism minimizes the sensing redundancy and maximizes the number of sleeping nodes in the network. We have also investigated the dynamic approach of activating sleeping nodes on-demand so that the moving target tracking accuracy can be enhanced while maximizing the network lifetime. We have carried out our extensive simulations in ns-3, and the results show that the proposed mechanism achieves higher performance compared to the state-of-the-art works.

  5. The dynamical evolution of binaries in clusters

    International Nuclear Information System (INIS)

    Heggie, D.C.

    1975-01-01

    Using information on the rates at which binaries suffer encounters in a stellar system (Heggie, 1974), the effects of such processes on the evolution of the system itself are studied. First considering systems with no binaries initially, it is shown that low-energy pairs attain a quasi-equilibrium distribution comparatively quickly. Their effect on the evolution of the cluster is negligible compared with that of two-body relaxation. In small systems energetic pairs may form sufficiently quickly to exercise a substantial effect on its development and on the escape rate, but in large systems their appearance is delayed until the evolution of the core is well advanced. In that case they appear to be responsible for arresting the collapse of the core at some stage. Binaries of low energy, even if present initially in large numbers, are likely to have at most only a temporary effect on the evolution of the system. High-energy pairs are not so easily destroyed, and so, if present initially, their effect is persistent. It competes with two-body relaxation especially when the fraction of such pairs and the total number-density are high, as in the core, where, in addition, binaries tend to congregate by mass segregation. When encounters with binaries become important, being mostly 'super-elastic' they enhance escape and lead to ejection of mass from the core into the halo, thus accelerating the rate at which mass is lost by tidal forces. It is difficult to decide observationally whether globular clusters possess sufficiently large numbers of binaries for these effects to be important. (Auth.)

  6. Dynamic Trajectory Extraction from Stereo Vision Using Fuzzy Clustering

    Science.gov (United States)

    Onishi, Masaki; Yoda, Ikushi

    In recent years, many human tracking researches have been proposed in order to analyze human dynamic trajectory. These researches are general technology applicable to various fields, such as customer purchase analysis in a shopping environment and safety control in a (railroad) crossing. In this paper, we present a new approach for tracking human positions by stereo image. We use the framework of two-stepped clustering with k-means method and fuzzy clustering to detect human regions. In the initial clustering, k-means method makes middle clusters from objective features extracted by stereo vision at high speed. In the last clustering, c-means fuzzy method cluster middle clusters based on attributes into human regions. Our proposed method can be correctly clustered by expressing ambiguity using fuzzy clustering, even when many people are close to each other. The validity of our technique was evaluated with the experiment of trajectories extraction of doctors and nurses in an emergency room of a hospital.

  7. Cooperation, clustering, and assortative mixing in dynamic networks.

    Science.gov (United States)

    Melamed, David; Harrell, Ashley; Simpson, Brent

    2018-01-30

    Humans' propensity to cooperate is driven by our embeddedness in social networks. A key mechanism through which networks promote cooperation is clustering. Within clusters, conditional cooperators are insulated from exploitation by noncooperators, allowing them to reap the benefits of cooperation. Dynamic networks, where ties can be shed and new ties formed, allow for the endogenous emergence of clusters of cooperators. Although past work suggests that either reputation processes or network dynamics can increase clustering and cooperation, existing work on network dynamics conflates reputations and dynamics. Here we report results from a large-scale experiment (total n = 2,675) that embedded participants in clustered or random networks that were static or dynamic, with varying levels of reputational information. Results show that initial network clustering predicts cooperation in static networks, but not in dynamic ones. Further, our experiment shows that while reputations are important for partner choice, cooperation levels are driven purely by dynamics. Supplemental conditions confirmed this lack of a reputation effect. Importantly, we find that when participants make individual choices to cooperate or defect with each partner, as opposed to a single decision that applies to all partners (as is standard in the literature on cooperation in networks), cooperation rates in static networks are as high as cooperation rates in dynamic networks. This finding highlights the importance of structured relations for sustained cooperation, and shows how giving experimental participants more realistic choices has important consequences for whether dynamic networks promote higher levels of cooperation than static networks.

  8. Range and damage distribution in cluster ion implantation

    International Nuclear Information System (INIS)

    Yamada, I.; Matsuo, J.; Jones, E.C.; Takeuchi, D.; Aoki, T.

    1997-01-01

    Cluster ion implantation is an attractive alternative to conventional ion implantation, particularly for shallow junction formation. It is easy to obtain high current ion beams with low equivalent energy using cluster ion beams. The implanted boron distribution in 5 keV B 10 H 14 implanted Si is markedly shallower than that in 5 keV BF 2 ion implanted Si. The implanted depth is less than 0.04 μm, indicating that cluster ion implantation is capable of forming shallow junctions. The sheet resistance of 3 keV B 10 H 14 implanted samples falls below 500 Ω/sq after annealing at 1,000 C for 10s. Shallow implantation can be realized by a high energy cluster beam without space-charge problems in the incident beam. Defect formation, resulting from local energy deposition and multiple collisions, is unique for cluster ions. The thickness of the damaged layer formed by cluster ion bombardment increases with the size of the cluster, if implant energy and ion dose remain constant. This is one of the nonlinear cluster effects, which may allow some control over the implant damage distributions that accompany implanted ions, and which have been shown to have a great effect on dopant redistribution during annealing

  9. Galaxy Cluster Mass Reconstruction Project - III. The impact of dynamical substructure on cluster mass estimates

    Science.gov (United States)

    Old, L.; Wojtak, R.; Pearce, F. R.; Gray, M. E.; Mamon, G. A.; Sifón, C.; Tempel, E.; Biviano, A.; Yee, H. K. C.; de Carvalho, R.; Müller, V.; Sepp, T.; Skibba, R. A.; Croton, D.; Bamford, S. P.; Power, C.; von der Linden, A.; Saro, A.

    2018-03-01

    With the advent of wide-field cosmological surveys, we are approaching samples of hundreds of thousands of galaxy clusters. While such large numbers will help reduce statistical uncertainties, the control of systematics in cluster masses is crucial. Here we examine the effects of an important source of systematic uncertainty in galaxy-based cluster mass estimation techniques: the presence of significant dynamical substructure. Dynamical substructure manifests as dynamically distinct subgroups in phase-space, indicating an `unrelaxed' state. This issue affects around a quarter of clusters in a generally selected sample. We employ a set of mock clusters whose masses have been measured homogeneously with commonly used galaxy-based mass estimation techniques (kinematic, richness, caustic, radial methods). We use these to study how the relation between observationally estimated and true cluster mass depends on the presence of substructure, as identified by various popular diagnostics. We find that the scatter for an ensemble of clusters does not increase dramatically for clusters with dynamical substructure. However, we find a systematic bias for all methods, such that clusters with significant substructure have higher measured masses than their relaxed counterparts. This bias depends on cluster mass: the most massive clusters are largely unaffected by the presence of significant substructure, but masses are significantly overestimated for lower mass clusters, by ˜ 10 per cent at 1014 and ≳ 20 per cent for ≲ 1013.5. The use of cluster samples with different levels of substructure can therefore bias certain cosmological parameters up to a level comparable to the typical uncertainties in current cosmological studies.

  10. Dynamic multifactor clustering of financial networks

    Science.gov (United States)

    Ross, Gordon J.

    2014-02-01

    We investigate the tendency for financial instruments to form clusters when there are multiple factors influencing the correlation structure. Specifically, we consider a stock portfolio which contains companies from different industrial sectors, located in several different countries. Both sector membership and geography combine to create a complex clustering structure where companies seem to first be divided based on sector, with geographical subclusters emerging within each industrial sector. We argue that standard techniques for detecting overlapping clusters and communities are not able to capture this type of structure and show how robust regression techniques can instead be used to remove the influence of both sector and geography from the correlation matrix separately. Our analysis reveals that prior to the 2008 financial crisis, companies did not tend to form clusters based on geography. This changed immediately following the crisis, with geography becoming a more important determinant of clustering structure.

  11. Advances in molecular vibrations and collision dynamics molecular clusters

    CERN Document Server

    Bacic, Zatko

    1998-01-01

    This volume focuses on molecular clusters, bound by van der Waals interactions and hydrogen bonds. Twelve chapters review a wide range of recent theoretical and experimental advances in the areas of cluster vibrations, spectroscopy, and reaction dynamics. The authors are leading experts, who have made significant contributions to these topics.The first chapter describes exciting results and new insights in the solvent effects on the short-time photo fragmentation dynamics of small molecules, obtained by combining heteroclusters with femtosecond laser excitation. The second is on theoretical work on effects of single solvent (argon) atom on the photodissociation dynamics of the solute H2O molecule. The next two chapters cover experimental and theoretical aspects of the energetics and vibrations of small clusters. Chapter 5 describes diffusion quantum Monte Carlo calculations and non additive three-body potential terms in molecular clusters. The next six chapters deal with hydrogen-bonded clusters, refle...

  12. Distributed fingerprint enhancement on a multicore cluster

    CSIR Research Space (South Africa)

    Khanyile, NP

    2012-07-01

    Full Text Available and memory distribution. Section 4 gives the algorithms description, while Section 5 introduces ways to deal with boundary pixels. Section 6 presents the performance analysis and Section 7 is devoted to conclusions and future works. 2. Background 2..., image enhancement is very crucial yet very computationally expensive. Sensing devices rarely produce perfect ready for use input images. Images are often corrupted by noise and by variations in fingerprint impression conditions. Image enhancement...

  13. Dynamic clustering and chemotactic collapse of self-phoretic active particles.

    Science.gov (United States)

    Pohl, Oliver; Stark, Holger

    2014-06-13

    Recent experiments with self-phoretic particles at low concentrations show a pronounced dynamic clustering [I. Theurkauff et al., Phys. Rev. Lett. 108, 268303 (2012)]. We model this situation by taking into account the translational and rotational diffusiophoretic motion, which the active particles perform in their self-generated chemical field. Our Brownian dynamics simulations show pronounced dynamic clustering only when these two phoretic contributions give rise to competing attractive and repulsive interactions, respectively. We identify two dynamic clustering states and characterize them by power-law-exponential distributions. In case of mere attraction a chemotactic collapse occurs directly from the gaslike into the collapsed state, which we also predict by mapping our Langevin dynamics on the Keller-Segel model for bacterial chemotaxis.

  14. Analysis of the dynamical cluster approximation for the Hubbard model

    OpenAIRE

    Aryanpour, K.; Hettler, M. H.; Jarrell, M.

    2002-01-01

    We examine a central approximation of the recently introduced Dynamical Cluster Approximation (DCA) by example of the Hubbard model. By both analytical and numerical means we study non-compact and compact contributions to the thermodynamic potential. We show that approximating non-compact diagrams by their cluster analogs results in a larger systematic error as compared to the compact diagrams. Consequently, only the compact contributions should be taken from the cluster, whereas non-compact ...

  15. DYNER: A DYNamic ClustER for Education and Research

    Science.gov (United States)

    Kehagias, Dimitris; Grivas, Michael; Mamalis, Basilis; Pantziou, Grammati

    2006-01-01

    Purpose: The purpose of this paper is to evaluate the use of a non-expensive dynamic computing resource, consisting of a Beowulf class cluster and a NoW, as an educational and research infrastructure. Design/methodology/approach: Clusters, built using commodity-off-the-shelf (COTS) hardware components and free, or commonly used, software, provide…

  16. Thermodynamics of small clusters of atoms: A molecular dynamics simulation

    DEFF Research Database (Denmark)

    Damgaard Kristensen, W.; Jensen, E. J.; Cotterill, Rodney M J

    1974-01-01

    The thermodynamic properties of clusters containing 55, 135, and 429 atoms have been calculated using the molecular dynamics method. Structural and vibrational properties of the clusters were examined at different temperatures in both the solid and the liquid phase. The nature of the melting...

  17. Influence of cluster mobility on Cu precipitation in α-Fe: A cluster dynamics modeling

    International Nuclear Information System (INIS)

    Jourdan, T.; Soisson, F.; Clouet, E.; Barbu, A.

    2010-01-01

    A cluster dynamics model has been parametrized to quantitatively reproduce results obtained by atomistic kinetic Monte Carlo (AKMC) modeling on the precipitation of Cu in α-Fe under thermal aging. The cluster mobility, highlighted by AKMC, is shown to have a significant effect on the precipitation kinetics and can reconcile the experimentally observed fast kinetics with the relatively low diffusivity of Cu monomers.

  18. Binary systems, star clusters and the Galactic-field population. Applied stellar dynamics

    Science.gov (United States)

    Kroupa, Pavel

    2002-01-01

    This book contains the results of recent theoretical work on the evolution of primordial binary systems in young star clusters, their effect on the evolution of their host clusters, implications for the distribution of young stars in the Milky Way, and the formation of bound star clusters. This work shows that if the Galactic-field binary population is a dynamically evolved version of the Taurus-Auriga pre-main sequence population, then most stars form in clusters with typically a few hundred binaries within a radius of about 0.5-1 pc. The results also suggest that the population I primordial binary-star orbital-parameter distribution functions may be universal, much like the initial mass function. Most solar-like planetary systems can survive in such clusters. The work presented here also establishes that most observed triple and quadruple systems must be primordial, but that α Cen A/B-Proxima Cen-like systems can form in clusters through dynamical capture. Precise N-body calculations using Aarseth's N-body codes of clusters containing up to 104 stars are used to create an extensive young-cluster library. These data demonstrate that the primordial binary systems are disrupted on a crossing-time scale, and that the truncation of the surviving period distribution measures the maximum concentration the cluster ever experienced. The N-body calculations demonstrate that Galactic star clusters form readily as nuclei of expanding OB associations despite a star-formation efficiency of typically 30 per cent and gas-expulsion over a time-span shorter than the cluster crossing time.

  19. Ananke: temporal clustering reveals ecological dynamics of microbial communities

    Directory of Open Access Journals (Sweden)

    Michael W. Hall

    2017-09-01

    Full Text Available Taxonomic markers such as the 16S ribosomal RNA gene are widely used in microbial community analysis. A common first step in marker-gene analysis is grouping genes into clusters to reduce data sets to a more manageable size and potentially mitigate the effects of sequencing error. Instead of clustering based on sequence identity, marker-gene data sets collected over time can be clustered based on temporal correlation to reveal ecologically meaningful associations. We present Ananke, a free and open-source algorithm and software package that complements existing sequence-identity-based clustering approaches by clustering marker-gene data based on time-series profiles and provides interactive visualization of clusters, including highlighting of internal OTU inconsistencies. Ananke is able to cluster distinct temporal patterns from simulations of multiple ecological patterns, such as periodic seasonal dynamics and organism appearances/disappearances. We apply our algorithm to two longitudinal marker gene data sets: faecal communities from the human gut of an individual sampled over one year, and communities from a freshwater lake sampled over eleven years. Within the gut, the segregation of the bacterial community around a food-poisoning event was immediately clear. In the freshwater lake, we found that high sequence identity between marker genes does not guarantee similar temporal dynamics, and Ananke time-series clusters revealed patterns obscured by clustering based on sequence identity or taxonomy. Ananke is free and open-source software available at https://github.com/beiko-lab/ananke.

  20. Emission of water clusters: molecular dynamic simulation

    International Nuclear Information System (INIS)

    Kutliev, U.O.; Kalandarov, K.S.

    2006-01-01

    Full text: Secondary ion mass spectrometry (SIMS) is a wonderful technique for providing mass spectrometric information of molecules on surfaces. Theoretical studies of the keV bombardment of organic films on metallic surfaces have contributed to our understanding of the mechanisms governing these processes. Many experiments of keV bombardment, however, are performed both thick and thin organic targets [1]. Molecular systems investigated experimentally by SIMS include adsorbed films on a metal substrate, molecular solids, polymers, or even biological cells. In this account, we focus on thin organic layers on metal substrates as they are used for analytical purposes, are intriguing from a fundamental viewpoint, and are computationally tractable [2]. There are we present molecular dynamics (MD) simulations aimed at obtaining such a microscopic picture and mass spectrum of sputtering particles. Because of the importance of H 2 O in many of the experiments, we have chosen it as our system. Water is also attractive as a system because of the extensive literature available on its physical properties. The interaction potentials available for MD simulations of H 2 O are sufficiently reliable such that a quantitative analysis of the simulation results can be directly related to the parameters of water. From the variety of substrate materials used in different experiments, we have chosen to perform our simulations using Au. This substance is chosen to match preliminary experiments with the selective killing of cells by inserted Au nanoparticles and because of the availability of good interaction potentials for gold. In the simulations, we bombarded by ions Ar the surface Au(III) covered by ice film. The interaction potential employed to describe the H 2 O-H 2 O interaction is the simple-point-charge (SPC) water potential developed by Berendsen et al. [3]. This potential has been used extensively to study the properties of H 2 O as a solid [4, 5]. It has been shown that the

  1. A mathematical model for the dynamics of clustering

    Science.gov (United States)

    Aeyels, Dirk; De Smet, Filip

    2008-10-01

    The formation of several clusters, arising from attracting forces between nonidentical entities or agents, is a phenomenon observed in diverse fields. Think of people gathered through a mutual interest, swarm behaviour of animals or clustering of oscillators in brain cells. We introduce a dynamic model of mutually attracting agents for which we prove that the long-term behaviour consists of agents organized into several groups or clusters. We have completely characterized the cluster structure (i.e. the number of clusters and their composition) by means of a set of inequalities in the parameters of the model and have identified the intensity of the attraction as a key parameter governing the transition between different cluster structures. The versatility of the model will be illustrated by discussing its relation to the Kuramoto model and by describing how it applies to a system of interconnected water basins.

  2. Multiscale electrical contact resistance in clustered contact distribution

    Science.gov (United States)

    Lee, Sangyoung; Cho, Hyun; Jang, Yong Hoon

    2009-08-01

    For contact between rough surfaces of conductors in which a clustered contact spot distribution is dominant through a multiscale process, electrical contact resistance (ECR) is analysed using a smoothed version of Greenwood's model (Jang and Barber 2003 J. Appl. Phys. 94 7215), which is extended to estimate the statistical distribution of contact spots considering the size and the location simultaneously. The application of this statistical method to a contact spot distribution, generated by the finite element method using a fractal surface defined by the random midpoint displacement algorithm, identifies the effect of the clustered contact distribution on ECR, showing that including a finer scale in the fractal contact surface causes the predicted resistance to approach a finite limit. It is also confirmed that the results are close to that of Barber's analogy (Barber 2003 Proc. R. Soc. Lond. A 459 53) regarding incremental stiffness and conductance for elastic contact.

  3. Gyration-radius dynamics in structural transitions of atomic clusters

    Science.gov (United States)

    Yanao, Tomohiro; Koon, Wang S.; Marsden, Jerrold E.; Kevrekidis, Ioannis G.

    2007-03-01

    This paper is concerned with the structural transition dynamics of the six-atom Morse cluster with zero total angular momentum, which serves as an illustrative example of the general reaction dynamics of isolated polyatomic molecules. It develops a methodology that highlights the interplay between the effects of the potential energy topography and those of the intrinsic geometry of the molecular internal space. The method focuses on the dynamics of three coarse variables, the molecular gyration radii. By using the framework of geometric mechanics and hyperspherical coordinates, the internal motions of a molecule are described in terms of these three gyration radii and hyperangular modes. The gyration radii serve as slow collective variables, while the remaining hyperangular modes serve as rapidly oscillating "bath" modes. Internal equations of motion reveal that the gyration radii are subject to two different kinds of forces: One is the ordinary force that originates from the potential energy function of the system, while the other is an internal centrifugal force. The latter originates from the dynamical coupling of the gyration radii with the hyperangular modes. The effects of these two forces often counteract each other: The potential force generally works to keep the internal mass distribution of the system compact and symmetric, while the internal centrifugal force works to inflate and elongate it. Averaged fields of these two forces are calculated numerically along a reaction path for the structural transition of the molecule in the three-dimensional space of gyration radii. By integrating the sum of these two force fields along the reaction path, an effective energy curve is deduced, which quantifies the gross work necessary for the system to change its mass distribution along the reaction path. This effective energy curve elucidates the energy-dependent switching of the structural preference between symmetric and asymmetric conformations. The present

  4. Exploring the Dynamics of Exoplanetary Systems in a Young Stellar Cluster

    Science.gov (United States)

    Thornton, Jonathan Daniel; Glaser, Joseph Paul; Wall, Joshua Edward

    2018-01-01

    I describe a dynamical simulation of planetary systems in a young star cluster. One rather arbitrary aspect of cluster simulations is the choice of initial conditions. These are typically chosen from some standard model, such as Plummer or King, or from a “fractal” distribution to try to model young clumpy systems. Here I adopt the approach of realizing an initial cluster model directly from a detailed magnetohydrodynamical model of cluster formation from a 1000-solar-mass interstellar gas cloud, with magnetic fields and radiative and wind feedback from massive stars included self-consistently. The N-body simulation of the stars and planets starts once star formation is largely over and feedback has cleared much of the gas from the region where the newborn stars reside. It continues until the cluster dissolves in the galactic field. Of particular interest is what would happen to the free-floating planets created in the gas cloud simulation. Are they captured by a star or are they ejected from the cluster? This method of building a dynamical cluster simulation directly from the results of a cluster formation model allows us to better understand the evolution of young star clusters and enriches our understanding of extrasolar planet development in them. These simulations were performed within the AMUSE simulation framework, and combine N-body, multiples and background potential code.

  5. Workload dynamics on clusters and grids

    NARCIS (Netherlands)

    Li, H.

    2009-01-01

    This paper presents a comprehensive statistical analysis of a variety of workloads collected on production clusters and Grids. The applications are mostly computational-intensive and each task requires single CPU for processing data, which dominate the workloads on current production Grid systems.

  6. Dynamics of globular cluster systems in elliptical galaxies

    NARCIS (Netherlands)

    Romanowsky, AJ; Geisler, D; Grebel, EK; Minniti, D

    2002-01-01

    One of the most promising avenues for exploring the dynamics of the outer parts of elliptical galaxies involves using bright discrete objects as kinematical tracers: globular clusters and planetary nebulae. As large data sets are becoming available, rigorous dynamical analyses are needed to

  7. Distribution of interatomic distances in large metallic clusters

    International Nuclear Information System (INIS)

    Glossman, M.D.; Iniguez, M.P.; Alonso, J.A.

    1992-01-01

    Spherically averaged pseudopotential (SAPS) calculations have been done for Mg n clusters, with n up to 250 within the framework of density functional theory. The electronic structure is computed resorting to the Thomas-Fermi-Dirac-Weizsaecker (TFDW) approximation for the kinetic energy. The equilibrium geometries have been obtained by minimizing the total cluster energy with respect to the atomic positions using the steepest-descent method. The ground state geometries obtained in this way are formed by spherical atomic shells, the number of them increasing with cluster size, up to a number of four for the biggest sizes considered here. An analysis of the distribution of the interatomic distances shows that the more internal is the shell, the more contracted are the interatomic distances. This effect diminishes progressively with increasing cluster size. For the purpose of comparison, similar calculations have been done with Cs n clusters in the same size range, allowing us to reproduce previous results obtained using a more elaborated density functional technique (Kohn-Sham method). The inhomogeneous contraction of interatomic distances then appears as a general fact for simple metallic clusters and not only for alkaline ones. (orig.)

  8. SSI-OSCAR: a Cluster Distribution for High Performance Computing Using a Single System Image

    OpenAIRE

    Vallée , Geoffroy; Scott , Stephen ,; Morin , Christine; Berthou , Jean-Yves; Prisker , Hugues

    2005-01-01

    The ease use and management of clusters needs tools to install, update and transparently manage distributed clusters resources. The management of clusters (node installations and updates) is a well-known problem and some high performance computing specific distributions are available today. These distributions, like OSCAR, allow users to install and manage clusters without specialized knowledge, allowing quick cluster deployment. The ease use of cluster is possible globally and transparently ...

  9. Jungle Computing: Distributed Supercomputing Beyond Clusters, Grids, and Clouds

    Science.gov (United States)

    Seinstra, Frank J.; Maassen, Jason; van Nieuwpoort, Rob V.; Drost, Niels; van Kessel, Timo; van Werkhoven, Ben; Urbani, Jacopo; Jacobs, Ceriel; Kielmann, Thilo; Bal, Henri E.

    In recent years, the application of high-performance and distributed computing in scientific practice has become increasingly wide spread. Among the most widely available platforms to scientists are clusters, grids, and cloud systems. Such infrastructures currently are undergoing revolutionary change due to the integration of many-core technologies, providing orders-of-magnitude speed improvements for selected compute kernels. With high-performance and distributed computing systems thus becoming more heterogeneous and hierarchical, programming complexity is vastly increased. Further complexities arise because urgent desire for scalability and issues including data distribution, software heterogeneity, and ad hoc hardware availability commonly force scientists into simultaneous use of multiple platforms (e.g., clusters, grids, and clouds used concurrently). A true computing jungle.

  10. On the equilibrium distribution of gas in clusters of galaxies

    Science.gov (United States)

    Lea, S. M.

    1975-01-01

    The hydrostatic-equilibrium solution for a polytropic gas in a cluster of galaxies has been calculated. The gas has a wider distribution than the galaxies. If the central gas density is 0.0008 particles/cu cm for gamma = 5/3 or 0.002 per cu cm for gamma = 1.35, the total X-ray emission from a model Coma cluster is equal to the observed emission. The spatial extent and spectrum for the source are also well-represented by the model if gamma = 1.35.

  11. Sensitivity evaluation of dynamic speckle activity measurements using clustering methods

    International Nuclear Information System (INIS)

    Etchepareborda, Pablo; Federico, Alejandro; Kaufmann, Guillermo H.

    2010-01-01

    We evaluate and compare the use of competitive neural networks, self-organizing maps, the expectation-maximization algorithm, K-means, and fuzzy C-means techniques as partitional clustering methods, when the sensitivity of the activity measurement of dynamic speckle images needs to be improved. The temporal history of the acquired intensity generated by each pixel is analyzed in a wavelet decomposition framework, and it is shown that the mean energy of its corresponding wavelet coefficients provides a suited feature space for clustering purposes. The sensitivity obtained by using the evaluated clustering techniques is also compared with the well-known methods of Konishi-Fujii, weighted generalized differences, and wavelet entropy. The performance of the partitional clustering approach is evaluated using simulated dynamic speckle patterns and also experimental data.

  12. Singular multiparameter dynamic equations with distributional ...

    African Journals Online (AJOL)

    In this paper, we consider both singular single and several multiparameter second order dynamic equations with distributional potentials on semi-innite time scales. At rst we construct Weyl's theory for the single singular multiparameter dynamic equation with distributional potentials and we prove that the forward jump of at ...

  13. Dynamic Extension of a Virtualized Cluster by using Cloud Resources

    International Nuclear Information System (INIS)

    Oberst, Oliver; Hauth, Thomas; Kernert, David; Riedel, Stephan; Quast, Günter

    2012-01-01

    The specific requirements concerning the software environment within the HEP community constrain the choice of resource providers for the outsourcing of computing infrastructure. The use of virtualization in HPC clusters and in the context of cloud resources is therefore a subject of recent developments in scientific computing. The dynamic virtualization of worker nodes in common batch systems provided by ViBatch serves each user with a dynamically virtualized subset of worker nodes on a local cluster. Now it can be transparently extended by the use of common open source cloud interfaces like OpenNebula or Eucalyptus, launching a subset of the virtual worker nodes within the cloud. This paper demonstrates how a dynamically virtualized computing cluster is combined with cloud resources by attaching remotely started virtual worker nodes to the local batch system.

  14. The Gas Distribution in the Outer Regions of Galaxy Clusters

    Science.gov (United States)

    Eckert, D.; Vazza, F.; Ettori, S.; Molendi, S.; Nagai, D.; Lau, E. T.; Roncarelli, M.; Rossetti, M.; Snowden, L.; Gastaldello, F.

    2012-01-01

    Aims. We present our analysis of a local (z = 0.04 - 0.2) sample of 31 galaxy clusters with the aim of measuring the density of the X-ray emitting gas in cluster outskirts. We compare our results with numerical simulations to set constraints on the azimuthal symmetry and gas clumping in the outer regions of galaxy clusters. Methods. We have exploited the large field-of-view and low instrumental background of ROSAT/PSPC to trace the density of the intracluster gas out to the virial radius, We stacked the density profiles to detect a signal beyond T200 and measured the typical density and scatter in cluster outskirts. We also computed the azimuthal scatter of the profiles with respect to the mean value to look for deviations from spherical symmetry. Finally, we compared our average density and scatter profiles with the results of numerical simulations. Results. As opposed to some recent Suzaku results, and confirming previous evidence from ROSAT and Chandra, we observe a steepening of the density profiles beyond approximately r(sub 500). Comparing our density profiles with simulations, we find that non-radiative runs predict density profiles that are too steep, whereas runs including additional physics and/ or treating gas clumping agree better with the observed gas distribution. We report high-confidence detection of a systematic difference between cool-core and non cool-core clusters beyond approximately 0.3r(sub 200), which we explain by a different distribution of the gas in the two classes. Beyond approximately r(sub 500), galaxy clusters deviate significantly from spherical symmetry, with only small differences between relaxed and disturbed systems. We find good agreement between the observed and predicted scatter profiles, but only when the 1% densest clumps are filtered out in the ENZO simulations. Conclusions. Comparing our results with numerical simulations, we find that non-radiative simulations fail to reproduce the gas distribution, even well outside

  15. The Gas Distribution in Galaxy Cluster Outer Regions

    Science.gov (United States)

    Eckert, D.; Vazza, F.; Ettori, S.; Molendi, S.; Nagai, D.; Laue, E. T.; Roncarelli, M.; Rossetti, M.; Snowden, S. L.; Gastaldello, F.

    2012-01-01

    Aims. We present the analysis of a local (z = 0.04 - 0.2) sample of 31 galaxy clusters with the aim of measuring the density of the X-ray emitting gas in cluster outskirts. We compare our results with numerical simulations to set constraints on the azimuthal symmetry and gas clumping in the outer regions of galaxy clusters. Methods. We exploit the large field-of-view and low instrumental background of ROSAT/PSPC to trace the density of the intracluster gas out to the virial radius. We perform a stacking of the density profiles to detect a signal beyond r200 and measure the typical density and scatter in cluster outskirts. We also compute the azimuthal scatter of the profiles with respect to the mean value to look for deviations from spherical symmetry. Finally, we compare our average density and scatter profiles with the results of numerical simulations. Results. As opposed to some recent Suzaku results, and confirming previous evidence from ROSAT and Chandra, we observe a steepening of the density profiles beyond approximately r(sub 500). Comparing our density profiles with simulations, we find that non-radiative runs predict too steep density profiles, whereas runs including additional physics and/or treating gas clumping are in better agreement with the observed gas distribution. We report for the first time the high-confidence detection of a systematic difference between cool-core and non-cool core clusters beyond 0.3r(sub 200), which we explain by a different distribution of the gas in the two classes. Beyond r(sub 500), galaxy clusters deviate significantly from spherical symmetry, with only little differences between relaxed and disturbed systems. We find good agreement between the observed and predicted scatter profiles, but only when the 1% densest clumps are filtered out in the simulations. Conclusions. Comparing our results with numerical simulations, we find that non-radiative simulations fail to reproduce the gas distribution, even well outside cluster

  16. MASSIVE CLUSTERS IN THE INNER REGIONS OF NGC 1365: CLUSTER FORMATION AND GAS DYNAMICS IN GALACTIC BARS

    International Nuclear Information System (INIS)

    Elmegreen, Bruce G.; Galliano, Emmanuel; Alloin, Danielle

    2009-01-01

    Cluster formation and gas dynamics in the central regions of barred galaxies are not well understood. This paper reviews the environment of three 10 7 M sun clusters near the inner Lindblad resonance (ILR) of the barred spiral NGC 1365. The morphology, mass, and flow of H I and CO gas in the spiral and barred regions are examined for evidence of the location and mechanism of cluster formation. The accretion rate is compared with the star formation rate to infer the lifetime of the starburst. The gas appears to move from inside corotation in the spiral region to looping filaments in the interbar region at a rate of ∼6 M sun yr -1 before impacting the bar dustlane somewhere along its length. The gas in this dustlane moves inward, growing in flux as a result of the accretion to ∼40 M sun yr -1 near the ILR. This inner rate exceeds the current nuclear star formation rate by a factor of 4, suggesting continued buildup of nuclear mass for another ∼0.5 Gyr. The bar may be only 1-2 Gyr old. Extrapolating the bar flow back in time, we infer that the clusters formed in the bar dustlane outside the central dust ring at a position where an interbar filament currently impacts the lane. The ram pressure from this impact is comparable to the pressure in the bar dustlane, and both are comparable to the pressure in the massive clusters. Impact triggering is suggested. The isothermal assumption in numerical simulations seems inappropriate for the rarefaction parts of spiral and bar gas flows. The clusters have enough lower-mass counterparts to suggest they are part of a normal power-law mass distribution. Gas trapping in the most massive clusters could explain their [Ne II] emission, which is not evident from the lower-mass clusters nearby.

  17. Method for discovering relationships in data by dynamic quantum clustering

    Science.gov (United States)

    Weinstein, Marvin; Horn, David

    2014-10-28

    Data clustering is provided according to a dynamical framework based on quantum mechanical time evolution of states corresponding to data points. To expedite computations, we can approximate the time-dependent Hamiltonian formalism by a truncated calculation within a set of Gaussian wave-functions (coherent states) centered around the original points. This allows for analytic evaluation of the time evolution of all such states, opening up the possibility of exploration of relationships among data-points through observation of varying dynamical-distances among points and convergence of points into clusters. This formalism may be further supplemented by preprocessing, such as dimensional reduction through singular value decomposition and/or feature filtering.

  18. Method for discovering relationships in data by dynamic quantum clustering

    Energy Technology Data Exchange (ETDEWEB)

    Weinstein, Marvin; Horn, David

    2017-05-09

    Data clustering is provided according to a dynamical framework based on quantum mechanical time evolution of states corresponding to data points. To expedite computations, we can approximate the time-dependent Hamiltonian formalism by a truncated calculation within a set of Gaussian wave-functions (coherent states) centered around the original points. This allows for analytic evaluation of the time evolution of all such states, opening up the possibility of exploration of relationships among data-points through observation of varying dynamical-distances among points and convergence of points into clusters. This formalism may be further supplemented by preprocessing, such as dimensional reduction through singular value decomposition and/or feature filtering.

  19. The next generation Virgo cluster survey. VIII. The spatial distribution of globular clusters in the Virgo cluster

    Energy Technology Data Exchange (ETDEWEB)

    Durrell, Patrick R.; Accetta, Katharine [Department of Physics and Astronomy, Youngstown State University, Youngstown, OH 44555 (United States); Côté, Patrick; Blakeslee, John P.; Ferrarese, Laura; McConnachie, Alan; Gwyn, Stephen [Herzberg Astronomy and Astrophysics, National Research Council, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Peng, Eric W.; Zhang, Hongxin [Department of Astronomy, Peking University, Beijing 100871 (China); Mihos, J. Christopher [Department of Astronomy, Case Western Reserve University, Cleveland, OH 44106 (United States); Puzia, Thomas H.; Jordán, Andrés [Institute of Astrophysics, Pontificia Universidad Catolica, Av. Vicu' a Mackenna 4860, Macul 7820436, Santiago (Chile); Lançon, Ariane [Observatoire astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550, 11 rue de l' Université, F-67000 Strasbourg (France); Liu, Chengze [Center for Astronomy and Astrophysics, Department of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240 (China); Cuillandre, Jean-Charles [Canada-France-Hawaii Telescope Corporation, Kamuela, HI 96743 (United States); Boissier, Samuel; Boselli, Alessandro [Aix Marseille Université, CNRS, LAM (Laboratoire d' Astrophysique de Marseille) UMR 7326, F-13388 Marseille (France); Courteau, Stéphane [Department of Physics, Engineering Physics and Astronomy, Queen' s University, Kingston, ON K7L 3N6 (Canada); Duc, Pierre-Alain [AIM Paris Saclay, CNRS/INSU, CEA/Irfu, Université Paris Diderot, Orme des Merisiers, F-91191 Gif sur Yvette cedex (France); Emsellem, Eric [Université de Lyon 1, CRAL, Observatoire de Lyon, 9 av. Charles André, F-69230 Saint-Genis Laval (France); CNRS, UMR 5574, ENS de Lyon (France); and others

    2014-10-20

    We report on a large-scale study of the distribution of globular clusters (GCs) throughout the Virgo cluster, based on photometry from the Next Generation Virgo Cluster Survey (NGVS), a large imaging survey covering Virgo's primary subclusters (Virgo A = M87 and Virgo B = M49) out to their virial radii. Using the g{sub o}{sup ′}, (g' – i') {sub o} color-magnitude diagram of unresolved and marginally resolved sources within the NGVS, we have constructed two-dimensional maps of the (irregular) GC distribution over 100 deg{sup 2} to a depth of g{sub o}{sup ′} = 24. We present the clearest evidence to date showing the difference in concentration between red and blue GCs over the full extent of the cluster, where the red (more metal-rich) GCs are largely located around the massive early-type galaxies in Virgo, while the blue (metal-poor) GCs have a much more extended spatial distribution with significant populations still present beyond 83' (∼215 kpc) along the major axes of both M49 and M87. A comparison of our GC maps to the diffuse light in the outermost regions of M49 and M87 show remarkable agreement in the shape, ellipticity, and boxiness of both luminous systems. We also find evidence for spatial enhancements of GCs surrounding M87 that may be indicative of recent interactions or an ongoing merger history. We compare the GC map to that of the locations of Virgo galaxies and the X-ray intracluster gas, and find generally good agreement between these various baryonic structures. We calculate the Virgo cluster contains a total population of N {sub GC} = 67, 300 ± 14, 400, of which 35% are located in M87 and M49 alone. For the first time, we compute a cluster-wide specific frequency S {sub N,} {sub CL} = 2.8 ± 0.7, after correcting for Virgo's diffuse light. We also find a GC-to-baryonic mass fraction ε {sub b} = 5.7 ± 1.1 × 10{sup –4} and a GC-to-total cluster mass formation efficiency ε {sub t} = 2.9 ± 0.5 × 10{sup –5

  20. Large Data Visualization on Distributed Memory Mulit-GPU Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Childs, Henry R.

    2010-03-01

    Data sets of immense size are regularly generated on large scale computing resources. Even among more traditional methods for acquisition of volume data, such as MRI and CT scanners, data which is too large to be effectively visualization on standard workstations is now commonplace. One solution to this problem is to employ a 'visualization cluster,' a small to medium scale cluster dedicated to performing visualization and analysis of massive data sets generated on larger scale supercomputers. These clusters are designed to fit a different need than traditional supercomputers, and therefore their design mandates different hardware choices, such as increased memory, and more recently, graphics processing units (GPUs). While there has been much previous work on distributed memory visualization as well as GPU visualization, there is a relative dearth of algorithms which effectively use GPUs at a large scale in a distributed memory environment. In this work, we study a common visualization technique in a GPU-accelerated, distributed memory setting, and present performance characteristics when scaling to extremely large data sets.

  1. Isomerization dynamics and thermodynamics of ionic argon clusters

    Science.gov (United States)

    Calvo, F.; Gadéa, F. X.; Lombardi, A.; Aquilanti, V.

    2006-09-01

    The dynamics and thermodynamics of small Arn+ clusters, n =3, 6, and 9, are investigated using molecular dynamics (MD) and exchange Monte Carlo (MC) simulations. A diatomic-in-molecule Hamiltonian provides an accurate model for the electronic ground state potential energy surface. The microcanonical caloric curves calculated from MD and MC methods are shown to agree with each other, provided that the rigorous conservation of angular momentum is accounted for in the phase space density of the MC simulations. The previously proposed projective partition of the kinetic energy is used to assist MD simulations in interpreting the cluster dynamics in terms of inertial, internal, and external modes. The thermal behavior is correlated with the nature of the charged core in the cluster by computing a dedicated charge localization order parameter. We also perform systematic quenches to establish a connection with the various isomers. We find that the Ar3+ cluster is very stable in its linear ground state geometry up to about 300K, and then isomerizes to a T-shaped isomer in which a quasineutral atom lies around a charged dimer. In Ar6+ and Ar9+, the covalent trimer core is solvated by neutral atoms, and the weakly bound solvent shell melts at much lower energies, occasionally leading to a tetramer or pentamer core with weakly charged extremities. At high energies the core itself becomes metastable and the cluster transforms into Ar2+ solvated by a fluid of neutral argon atoms.

  2. Complexity functions for networks: Dynamical hubs and complexity clusters

    Science.gov (United States)

    Afraimovich, Valentin; Dmitrichev, Aleksei; Shchapin, Dmitry; Nekorkin, Vladimir

    2018-02-01

    A method for studying the behavior of the elements of dynamical networks is introduced. We measure the amount of instability stored at each element according to the value of the mean complexity related to this element. Elements with close values of the mean complexity can be unified into complexity clusters; elements with the smallest values of complexities form dynamical hubs. The effectiveness of the method is manifested by its successive application to networks of coupled Lorenz systems.

  3. Parallel Genetic Algorithms with Dynamic Topology using Cluster Computing

    Directory of Open Access Journals (Sweden)

    ADAR, N.

    2016-08-01

    Full Text Available A parallel genetic algorithm (PGA conducts a distributed meta-heuristic search by employing genetic algorithms on more than one subpopulation simultaneously. PGAs migrate a number of individuals between subpopulations over generations. The layout that facilitates the interactions of the subpopulations is called the topology. Static migration topologies have been widely incorporated into PGAs. In this article, a PGA with a dynamic migration topology (D-PGA is proposed. D-PGA generates a new migration topology in every epoch based on the average fitness values of the subpopulations. The D-PGA has been tested against ring and fully connected migration topologies in a Beowulf Cluster. The D-PGA has outperformed the ring migration topology with comparable communication cost and has provided competitive or better results than a fully connected migration topology with significantly lower communication cost. PGA convergence behaviors have been analyzed in terms of the diversities within and between subpopulations. Conventional diversity can be considered as the diversity within a subpopulation. A new concept of permeability has been introduced to measure the diversity between subpopulations. It is shown that the success of the proposed D-PGA can be attributed to maintaining a high level of permeability while preserving diversity within subpopulations.

  4. Metal cluster fission: jellium model and Molecular dynamics simulations

    DEFF Research Database (Denmark)

    Lyalin, Andrey G.; Obolensky, Oleg I.; Solov'yov, Ilia

    2004-01-01

    Fission of doubly charged sodium clusters is studied using the open-shell two-center deformed jellium model approximation and it ab initio molecular dynamic approach accounting for all electrons in the system. Results of calculations of fission reactions Na_10^2+ --> Na_7^+ + Na_3^+ and Na_18...

  5. Binary Populations and Stellar Dynamics in Young Clusters

    Science.gov (United States)

    Vanbeveren, D.; Belkus, H.; Van Bever, J.; Mennekens, N.

    2008-06-01

    We first summarize work that has been done on the effects of binaries on theoretical population synthesis of stars and stellar phenomena. Next, we highlight the influence of stellar dynamics in young clusters by discussing a few candidate UFOs (unconventionally formed objects) like intermediate mass black holes, η Car, ζ Pup, γ2 Velorum and WR 140.

  6. Dynamics of Stars and Globular Clusters in Galaxy Halos

    NARCIS (Netherlands)

    Romanowsky, Aaron J.; Douglas, Nigel G.; Kuijken, Konrad; Arnaboldi, Magda; Kissler-Patig, Markus; Sharples, Ray M.; Zepf, Stephen E.; Rhode, Katherine L.; Kissler-Patig, M.

    2003-01-01

    We have obtained kinematical data in the halos of the giant ellipticals M49 and M87. These include globular cluster velocities in M49 to 10 R_eff and planetary nebula velocities in M49 and M87 to 4 R_eff. We report initial results, including dynamical comparisons between the diffuse stellar

  7. Exploring personality clusters among parents of ED subjects. Relationship with parents' psychopathology, attachment, and family dynamics.

    Science.gov (United States)

    Amianto, Federico; Daga, Giovanni Abbate; Bertorello, Antonella; Fassino, Secondo

    2013-10-01

    Eating disorders are some of the most difficult mental disorders to treat and manage. Family interacts with genetic dispositions and other pathogenic factors, and may influence the outburst, development and outcome of EDs. The present study explores with a cluster analysis the personality traits of parents of ED subjects. One-hundred-eight mothers and 104 fathers were tested with Temperament Character Inventory (TCI), Eating Disorder Inventory-2 (EDI-2), State-Trait Anger Expression Inventory (STAX), Family Assessment Device (FAD), Attachment Style Questionnaire (ASQ), Symptom Questionnaire (SQ), Psychological Well-Being scales (PWB). The cluster distribution of parents based on personality traits was explored. Parents' clusters TCI scores were compared as regards personality, psychopathology, attachment and family features. Cross distribution of temperament and character clusters in mothers and fathers, among couples and ED diagnoses of the daughters was explored. Two clusters of mothers and fathers were identified with temperament clustering. Character traits led to two mothers and three fathers clusters. Mothers temperament cluster 1 (MTC1) correspond to a explosive/adventurous profile, MTC2 to a cautious/passive-dependent profile. Fathers temperament cluster 1 (FTC1) was explosive/methodic, FTC2 was independent/methodic. Character clustering distinguished very immature mothers (MCC1) and majority (65%) of character mature mothers with low self-transcendence (MCC2). A third of fathers was severely immature (FCC1), a third impaired as regards relationships (poor cooperativeness and self-transcendence; FCC2), and one third character mature fathers with low self-transcendence (FCC3). Each cluster evidences specific psychopathology and attachment characteristics. FTC1 was more frequently associated with character immaturity. No significant clusters' cross correlation was found in parental couples. Parents' clusters analyze in depth the univocal picture of

  8. Nonlocal Coulomb correlations in pure and electron-doped Sr2IrO4 : Spectral functions, Fermi surface, and pseudo-gap-like spectral weight distributions from oriented cluster dynamical mean-field theory

    Science.gov (United States)

    Martins, Cyril; Lenz, Benjamin; Perfetti, Luca; Brouet, Veronique; Bertran, François; Biermann, Silke

    2018-03-01

    We address the role of nonlocal Coulomb correlations and short-range magnetic fluctuations in the high-temperature phase of Sr2IrO4 within state-of-the-art spectroscopic and first-principles theoretical methods. Introducing an "oriented-cluster dynamical mean-field scheme", we compute momentum-resolved spectral functions, which we find to be in excellent agreement with angle-resolved photoemission spectra. We show that while short-range antiferromagnetic fluctuations are crucial to accounting for the electronic properties of Sr2IrO4 even in the high-temperature paramagnetic phase, long-range magnetic order is not a necessary ingredient of the insulating state. Upon doping, an exotic metallic state is generated, exhibiting cuprate-like pseudo-gap spectral properties, for which we propose a surprisingly simple theoretical mechanism.

  9. Dynamics, Chemical Abundances, and ages of Globular Clusters in the Virgo Cluster of Galaxies

    Science.gov (United States)

    Guhathakurta, Puragra; NGVS Collaboration

    2018-01-01

    We present a study of the dynamics, metallicities, and ages of globular clusters (GCs) in the Next Generation Virgo cluster Survey (NGVS), a deep, multi-band (u, g, r, i, z, and Ks), wide-field (104 deg2) imaging survey carried out using the 3.6-m Canada-France-Hawaii Telescope and MegaCam imager. GC candidates were selected from the NGVS survey using photometric and image morphology criteria and these were followed up with deep, medium-resolution, multi-object spectroscopy using the Keck II 10-m telescope and DEIMOS spectrograph. The primary spectroscopic targets were candidate GC satellites of dwarf elliptical (dE) and ultra-diffuse galaxies (UDGs) in the Virgo cluster. While many objects were confirmed as GC satellites of Virgo dEs and UDGs, many turned out to be non-satellites based on their radial velocity and/or positional mismatch any identifiable Virgo cluster galaxy. We have used a combination of spectral characteristics (e.g., presence of absorption vs. emission lines), new Gaussian mixture modeling of radial velocity and sky position data, and a new extreme deconvolution analysis of ugrizKs photometry and image morphology, to classify all the objects in our sample into: (1) GC satellites of dE galaxies, (2) GC satellites of UDGs, (3) intra-cluster GCs (ICGCs) in the Virgo cluster, (4) GCs in the outer halo of the central cluster galaxy M87, (5) foreground Milky Way stars, and (6) distant background galaxies. We use these data to study the dynamics and dark matter content of dE and UDGs in the Virgo cluster, place important constraints on the nature of dE nuclei, and study the origin of ICGCs versus GCs in the remote M87 halo.We are grateful for financial support from the NSF and NASA/STScI.

  10. mocca code for star cluster simulations - VI. Bimodal spatial distribution of blue stragglers

    Science.gov (United States)

    Hypki, Arkadiusz; Giersz, Mirek

    2017-11-01

    The paper presents an analysis of formation mechanism and properties of spatial distributions of blue stragglers in evolving globular clusters, based on numerical simulations done with the mocca code. First, there are presented N-body and mocca simulations which try to reproduce the simulations presented by Ferraro et al. (2012). Then, we show the agreement between N-body and the mocca code. Finally, we discuss the formation process of the bimodal distribution. We report that we could not reproduce simulations from Ferraro et al. (2012). Moreover, we show that the so-called bimodal spatial distribution of blue stragglers is a very transient feature. It is formed for one snapshot in time and it can easily vanish in the next one. Moreover, we show that the radius of avoidance proposed by Ferraro et al. (2012) goes out of sync with the apparent minimum of the bimodal distribution after about two half-mass relaxation times (without finding out what is the reason for that). This finding creates a real challenge for the dynamical clock, which uses this radius to determine the dynamical age of globular clusters. Additionally, the paper discusses a few important problems concerning the apparent visibilities of the bimodal distributions, which have to be taken into account while studying the spatial distributions of blue stragglers.

  11. Analysis of the structure and dynamics of the stellar tails of open star clusters

    Science.gov (United States)

    Chumak, Ya. O.; Rastorguev, A. S.

    2006-03-01

    We have analyzed the formation, structure, and dynamical evolution of the population of stars that escaped from open clusters by numerical simulations using S. Aarseth’s modified NBODY6 code. In the Galactic tidal field, the population of stars that escaped from a cluster is shown to be elongated along the orbit of the cluster symmetrically about its core in the form of stellar tails of increasing sizes. We analyze the parameters of stellar tails as a function of such initial simulation conditions as the number of stars, the cluster density, the eccentricity of the Galactic cluster orbit in the plane of the Galactic disk, and the z velocity component. As a result, we constructed a grid of model stellar tails of open clusters. The grid includes such time-dependent parameters of the stellar tails as the length, the cross section, the number of stars, the velocity distribution, etc. Our simulations allow us to clarify the origin of moving clusters and stellar streams and to assess the role of star clusters in forming the stellar velocity field in the solar neighborhood.

  12. Clustering Effect on the Dynamics in a Spatial Rock-Paper-Scissors System

    Science.gov (United States)

    Hashimoto, Tsuyoshi; Sato, Kazunori; Ichinose, Genki; Miyazaki, Rinko; Tainaka, Kei-ichi

    2018-01-01

    The lattice dynamics for rock-paper-scissors games is related to population theories in ecology. In most cases, simulations are performed by local and global interactions. It is known in the former case that the dynamics is usually stable. We find two types of non-random distributions in the stationary state. One is a cluster formation of endangered species: when the density of a species approaches zero, its clumping degree diverges to infinity. The other is the strong aggregations of high-density species. Such spatial pattern formations play important roles in population dynamics.

  13. Cluster Optimization and Parallelization of Simulations with Dynamically Adaptive Grids

    KAUST Repository

    Schreiber, Martin

    2013-01-01

    The present paper studies solvers for partial differential equations that work on dynamically adaptive grids stemming from spacetrees. Due to the underlying tree formalism, such grids efficiently can be decomposed into connected grid regions (clusters) on-the-fly. A graph on those clusters classified according to their grid invariancy, workload, multi-core affinity, and further meta data represents the inter-cluster communication. While stationary clusters already can be handled more efficiently than their dynamic counterparts, we propose to treat them as atomic grid entities and introduce a skip mechanism that allows the grid traversal to omit those regions completely. The communication graph ensures that the cluster data nevertheless are kept consistent, and several shared memory parallelization strategies are feasible. A hyperbolic benchmark that has to remesh selected mesh regions iteratively to preserve conforming tessellations acts as benchmark for the present work. We discuss runtime improvements resulting from the skip mechanism and the implications on shared memory performance and load balancing. © 2013 Springer-Verlag.

  14. Cluster Dynamics Modeling with Bubble Nucleation, Growth and Coalescence

    Energy Technology Data Exchange (ETDEWEB)

    de Almeida, Valmor F. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Blondel, Sophie [Univ. of Tennessee, Knoxville, TN (United States); Bernholdt, David E. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Wirth, Brian D. [Univ. of Tennessee, Knoxville, TN (United States)

    2017-06-01

    The topic of this communication pertains to defect formation in irradiated solids such as plasma-facing tungsten submitted to helium implantation in fusion reactor com- ponents, and nuclear fuel (metal and oxides) submitted to volatile ssion product generation in nuclear reactors. The purpose of this progress report is to describe ef- forts towards addressing the prediction of long-time evolution of defects via continuum cluster dynamics simulation. The di culties are twofold. First, realistic, long-time dynamics in reactor conditions leads to a non-dilute di usion regime which is not accommodated by the prevailing dilute, stressless cluster dynamics theory. Second, long-time dynamics calls for a large set of species (ideally an in nite set) to capture all possible emerging defects, and this represents a computational bottleneck. Extensions beyond the dilute limit is a signi cant undertaking since no model has been advanced to extend cluster dynamics to non-dilute, deformable conditions. Here our proposed approach to model the non-dilute limit is to monitor the appearance of a spatially localized void volume fraction in the solid matrix with a bell shape pro le and insert an explicit geometrical bubble onto the support of the bell function. The newly cre- ated internal moving boundary provides the means to account for the interfacial ux of mobile species into the bubble, and the growth of bubbles allows for coalescence phenomena which captures highly non-dilute interactions. We present a preliminary interfacial kinematic model with associated interfacial di usion transport to follow the evolution of the bubble in any number of spatial dimensions and any number of bubbles, which can be further extended to include a deformation theory. Finally we comment on a computational front-tracking method to be used in conjunction with conventional cluster dynamics simulations in the non-dilute model proposed.

  15. Spatial distribution and cluster analysis of sexual risk behaviors reported by young men in Kisumu, Kenya

    Directory of Open Access Journals (Sweden)

    Parker Corette

    2010-05-01

    Full Text Available Abstract Background The well-established connection between HIV risk behavior and place of residence points to the importance of geographic clustering in the potential transmission of HIV and other sexually transmitted infections (STI. Methods To investigate the geospatial distribution of prevalent sexually transmitted infections and sexual behaviors in a sample of 18-24 year-old sexually active men in urban and rural areas of Kisumu, Kenya, we mapped the residences of 649 men and conducted spatial cluster analysis. Spatial distribution of the study participants was assessed in terms of the demographic, behavioral, and sexual dysfunction variables, as well as laboratory diagnosed STIs. To test for the presence and location of clusters we used Kulldorff's spatial scan statistic as implemented in the Satscan program. Results The results of this study suggest that sexual risk behaviors and STIs are evenly distributed in our sample throughout the Kisumu district. No behavioral or STI clusters were detected, except for condom use. Neither urban nor rural residence significantly impacted risk behavior or STI prevalence. Conclusion We found no association between place of residence and sexual risk behaviors in our sample. While our results can not be generalized to other populations, the study shows that geospatial analysis can be an important tool for investigating study sample characteristics; for evaluating HIV/STI risk factors; and for development and implementation of targeted HIV and STI control programs in specifically defined populations and in areas where the underlying population dynamic is poorly understood.

  16. The dynamical evolution of a young star cluster

    Science.gov (United States)

    Kroupa, P.

    Observations show that the Trapezium Cluster in Orion is at most 1 Myr old, very dense, and containing about six OB stars at its centre. About 50 per cent or more of the cluster stars are binary systems. It may be expanding rapidly due to very recent gas blow-out, or it may be near virial equilibrium, or in cold collapse. The dynamics of the cluster is interesting because (i) it may be too young for dynamical evolution to have established the observed degree of mass segregation, and (ii) the binary population may still be young enough not to have been affected significantly by dynamical evolution. If both are true, then we have evidence that massive stars form at the centres of rich embedded clusters and that the binary proportion varies with star-forming conditions. A number of N-body calculations of model, binary-rich Trapezium Clusters have been performed using Aarseth's Nbody5 programme (Kroupa, Petr & McCaughrean 1998). Here, attention is focused on models in which the star formation efficiency was 50 per cent with instantaneous mass loss. It is found that the model central density and velocity dispersion agree with the observational constraints if expansion is only about 6x10^4 yr old. Additionally, the observed binary proportion constrains the primordial proportion to have been significantly less than in Taurus--Auriga. However, if variation of the birth binary proportion with gas cloud parameters has been detected can only be verified if the cluster can be shown to be expanding rapidly.

  17. Dynamic analysis of clustered building structures using substructures methods

    International Nuclear Information System (INIS)

    Leimbach, K.R.; Krutzik, N.J.

    1989-01-01

    The dynamic substructure approach to the building cluster on a common base mat starts with the generation of Ritz-vectors for each building on a rigid foundation. The base mat plus the foundation soil is subjected to kinematic constraint modes, for example constant, linear, quadratic or cubic constraints. These constraint modes are also imposed on the buildings. By enforcing kinematic compatibility of the complete structural system on the basis of the constraint modes a reduced Ritz model of the complete cluster is obtained. This reduced model can now be analyzed by modal time history or response spectrum methods

  18. Halo Occupation Distribution Modeling of Clustering of Luminous Red Galaxies

    OpenAIRE

    Zheng, Zheng; Zehavi, Idit; Eisenstein, Daniel J.; Weinberg, David H.; Jing, Y. P.

    2008-01-01

    We perform Halo Occupation Distribution (HOD) modeling to interpret small-scale and intermediate-scale clustering of 35,000 luminous early-type galaxies and their cross-correlation with a reference imaging sample of normal L* galaxies in the Sloan Digital Sky Survey. The modeling results show that most of these luminous red galaxies (LRGs) are central galaxies residing in massive halos of typical mass M ~ a few times 10^13 to 10^14 Msun/h, while a few percent of them have to be satellites wit...

  19. Cluster-based Dynamic Energy Management for Collaborative Target Tracking in Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Dao-Wei Bi

    2007-07-01

    Full Text Available A primary criterion of wireless sensor network is energy efficiency. Focused onthe energy problem of target tracking in wireless sensor networks, this paper proposes acluster-based dynamic energy management mechanism. Target tracking problem isformulated by the multi-sensor detection model as well as energy consumption model. Adistributed adaptive clustering approach is investigated to form a reasonable routingframework which has uniform cluster head distribution. Dijkstra’s algorithm is utilized toobtain optimal intra-cluster routing. Target position is predicted by particle filter. Thepredicted target position is adopted to estimate the idle interval of sensor nodes. Hence,dynamic awakening approach is exploited to prolong sleep time of sensor nodes so that theoperation energy consumption of wireless sensor network can be reduced. The sensornodes around the target wake up on time and act as sensing candidates. With the candidatesensor nodes and predicted target position, the optimal sensor node selection is considered.Binary particle swarm optimization is proposed to minimize the total energy consumptionduring collaborative sensing and data reporting. Experimental results verify that theproposed clustering approach establishes a low-energy communication structure while theenergy efficiency of wireless sensor networks is enhanced by cluster-based dynamic energymanagement.

  20. High-performance dynamic quantum clustering on graphics processors

    International Nuclear Information System (INIS)

    Wittek, Peter

    2013-01-01

    Clustering methods in machine learning may benefit from borrowing metaphors from physics. Dynamic quantum clustering associates a Gaussian wave packet with the multidimensional data points and regards them as eigenfunctions of the Schrödinger equation. The clustering structure emerges by letting the system evolve and the visual nature of the algorithm has been shown to be useful in a range of applications. Furthermore, the method only uses matrix operations, which readily lend themselves to parallelization. In this paper, we develop an implementation on graphics hardware and investigate how this approach can accelerate the computations. We achieve a speedup of up to two magnitudes over a multicore CPU implementation, which proves that quantum-like methods and acceleration by graphics processing units have a great relevance to machine learning.

  1. Functional clustering algorithm for the analysis of dynamic network data

    Science.gov (United States)

    Feldt, S.; Waddell, J.; Hetrick, V. L.; Berke, J. D.; Żochowski, M.

    2009-05-01

    We formulate a technique for the detection of functional clusters in discrete event data. The advantage of this algorithm is that no prior knowledge of the number of functional groups is needed, as our procedure progressively combines data traces and derives the optimal clustering cutoff in a simple and intuitive manner through the use of surrogate data sets. In order to demonstrate the power of this algorithm to detect changes in network dynamics and connectivity, we apply it to both simulated neural spike train data and real neural data obtained from the mouse hippocampus during exploration and slow-wave sleep. Using the simulated data, we show that our algorithm performs better than existing methods. In the experimental data, we observe state-dependent clustering patterns consistent with known neurophysiological processes involved in memory consolidation.

  2. Photodetachment and dissociation dynamics of microsolvated iodide clusters

    Energy Technology Data Exchange (ETDEWEB)

    Piani, G; Becucci, M [European Laboratory for Non-Linear Spectroscopy, Polo Scientifico e Tecnologico Universita di Firenze, via N Carrara 1, 50019 Sesto Fiorentino (Italy); Bowen, M S; Oakman, J; Hu, Q; Continetti, R E [Department of Chemistry and Biochemistry, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0340 (United States)], E-mail: gpiani@lens.unifi.it, E-mail: becucci@lens.unifi.it, E-mail: rcontinetti@ucsd.edu

    2008-11-15

    The properties of anionic clusters I{sup -}X (X=carbon dioxide, water, ammonia, benzene, phenol, aniline and nitrobenzene) and their dissociation dynamics on the neutral potential energy surface following photodetachment (PD) were studied by photoelectron-photofragment coincidence experiments. Different reaction channels were available using 4.82 eV energy photons, leading to production of iodine in the {sup 2}P{sub 3/2} and {sup 2}P{sub 1/2} states and to both stable and dissociating neutral clusters. The partitioning of the available energy strongly favors the electron kinetic energy channel. The kinetic energy release in the fragment channel is rather small and dependent on the potential energy surface on which the process takes place. A multistep dissociative PD process is observed for the iodide-aniline cluster leading to production of zero kinetic energy electrons.

  3. Stochastic dynamics of spatial effects in fragmentation of clusters

    International Nuclear Information System (INIS)

    Salinas-Rodriguez, E.; Rodriguez, R.F.; Zamora, J.M.

    1991-01-01

    We use a stochastic approach to study the effects of spatial in homogeneities in the kinetics of a fragmentation model which occurs in cluster breakup and polymer degradation. The analytical form of the cluster size distribution function is obtained for both the discrete and continuous limits. From it we calculate numerically the average size and volume of the clusters, their total concentration and the total scattering of the dispersion in both limits. The influence of spatial effects is explicitly shown in the last two quantities. From our description the equations for the equal-time and the two times density correlation functions are also derived in the continuous limit. Finally, the perspectives and limitations of our approach are discussed (Author)

  4. Dynamic object management for distributed data structures

    Science.gov (United States)

    Totty, Brian K.; Reed, Daniel A.

    1992-01-01

    In distributed-memory multiprocessors, remote memory accesses incur larger delays than local accesses. Hence, insightful allocation and access of distributed data can yield substantial performance gains. The authors argue for the use of dynamic data management policies encapsulated within individual distributed data structures. Distributed data structures offer performance, flexibility, abstraction, and system independence. This approach is supported by data from a trace-driven simulation study of parallel scientific benchmarks. Experimental data on memory locality, message count, message volume, and communication delay suggest that data-structure-specific data management is superior to a single, system-imposed policy.

  5. Global Analysis of miRNA Gene Clusters and Gene Families Reveals Dynamic and Coordinated Expression

    Directory of Open Access Journals (Sweden)

    Li Guo

    2014-01-01

    Full Text Available To further understand the potential expression relationships of miRNAs in miRNA gene clusters and gene families, a global analysis was performed in 4 paired tumor (breast cancer and adjacent normal tissue samples using deep sequencing datasets. The compositions of miRNA gene clusters and families are not random, and clustered and homologous miRNAs may have close relationships with overlapped miRNA species. Members in the miRNA group always had various expression levels, and even some showed larger expression divergence. Despite the dynamic expression as well as individual difference, these miRNAs always indicated consistent or similar deregulation patterns. The consistent deregulation expression may contribute to dynamic and coordinated interaction between different miRNAs in regulatory network. Further, we found that those clustered or homologous miRNAs that were also identified as sense and antisense miRNAs showed larger expression divergence. miRNA gene clusters and families indicated important biological roles, and the specific distribution and expression further enrich and ensure the flexible and robust regulatory network.

  6. Dynamical evolution of stars and gas of young embedded stellar sub-clusters

    Science.gov (United States)

    Sills, Alison; Rieder, Steven; Scora, Jennifer; McCloskey, Jessica; Jaffa, Sarah

    2018-03-01

    We present simulations of the dynamical evolution of young embedded star clusters. Our initial conditions are directly derived from X-ray, infrared, and radio observations of local systems, and our models evolve both gas and stars simultaneously. Our regions begin with both clustered and extended distributions of stars, and a gas distribution which can include a filamentary structure in addition to gas surrounding the stellar subclusters. We find that the regions become spherical, monolithic, and smooth quite quickly, and that the dynamical evolution is dominated by the gravitational interactions between the stars. In the absence of stellar feedback, the gas moves gently out of the centre of our regions but does not have a significant impact on the motions of the stars at the earliest stages of cluster formation. Our models at later times are consistent with observations of similar regions in the local neighbourhood. We conclude that the evolution of young proto-star clusters is relatively insensitive to reasonable choices of initial conditions. Models with more realism, such as an initial population of binary and multiple stars and ongoing star formation, are the next step needed to confirm these findings.

  7. Coupled dynamic analysis of a single gimbal control moment gyro cluster integrated with an isolation system

    Science.gov (United States)

    Luo, Qing; Li, Dongxu; Jiang, Jianping

    2014-01-01

    Control moment gyros (CMGs) are widely used as actuators for attitude control in spacecraft. However, micro-vibrations produced by CMGs will degrade the pointing performance of high-sensitivity instruments on-board the spacecraft. This paper addresses dynamic modelling and performs an analysis on the micro-vibration isolation for a single gimbal CMG (SGCMG) cluster. First, an analytical model was developed to describe both the coupled SGCMG cluster and the multi-axis isolation system that can express the dynamic outputs. This analytical model accurately reflects the mass and inertia properties, the gyroscopic effects and flexible modes of the coupled system, which can be generalized for isolation applications of SGCMG clusters. Second, the analytical model was validated using MSC.NASTRAN software based on the finite element technique. The dynamic characteristics of the coupled system are affected by the mass distribution and the gyroscopic effects of the SGCMGs. The gyroscopic effects produced by the rotary flywheel will stiffen or soften several of the structural modes of the coupled system. In addition, the gyroscopic effect of each SGCMG can interact with or counteract that of others, which induce vibration modes coupled together. Finally, the performance of the passive isolation was analysed. It was demonstrated that the gyroscopic effects should be considered in isolation studies on SGCMG clusters; otherwise, the isolation performance will be underestimated if they are ignored.

  8. Dynamics of the young binary LMC cluster NGC 1850

    Science.gov (United States)

    Fischer, Philippe; Welch, Douglas L.; Mateo, Mario

    1993-01-01

    BV CCD images and echelle spectra of 52 supergiants are used to examine the age and internal dynamics of the young binary LMC cluster NGC 1850. A color-magnitude diagram was constructed and found to contain three distinct populations of stars. Using star-subtracted, median filtered BV images, attempts were made to determine ellipticity parameters, BV luminosity profiles were constructed to project radii greater than 40. A power law model was applied to test for the presence of a tidal cutoff in the luminosity profile. Of the 52 stars with echelle spectra, a subset of 36 were used to study the cluster dynamics. A rotational signal in the radial velocities has been detected at the 93-percent confidence level, implying a rotation axis at a position angle of 100 +/- 40 deg. Values for the slope of the mass function were determined using mass luminosity relationships and different forms for the IMF. The current cluster age is similar to its central relaxation time.

  9. A mathematical programming approach for sequential clustering of dynamic networks

    Science.gov (United States)

    Silva, Jonathan C.; Bennett, Laura; Papageorgiou, Lazaros G.; Tsoka, Sophia

    2016-02-01

    A common analysis performed on dynamic networks is community structure detection, a challenging problem that aims to track the temporal evolution of network modules. An emerging area in this field is evolutionary clustering, where the community structure of a network snapshot is identified by taking into account both its current state as well as previous time points. Based on this concept, we have developed a mixed integer non-linear programming (MINLP) model, SeqMod, that sequentially clusters each snapshot of a dynamic network. The modularity metric is used to determine the quality of community structure of the current snapshot and the historical cost is accounted for by optimising the number of node pairs co-clustered at the previous time point that remain so in the current snapshot partition. Our method is tested on social networks of interactions among high school students, college students and members of the Brazilian Congress. We show that, for an adequate parameter setting, our algorithm detects the classes that these students belong more accurately than partitioning each time step individually or by partitioning the aggregated snapshots. Our method also detects drastic discontinuities in interaction patterns across network snapshots. Finally, we present comparative results with similar community detection methods for time-dependent networks from the literature. Overall, we illustrate the applicability of mathematical programming as a flexible, adaptable and systematic approach for these community detection problems. Contribution to the Topical Issue "Temporal Network Theory and Applications", edited by Petter Holme.

  10. Exploring Sources of Gravitational Waves From Star Cluster Dynamics

    Science.gov (United States)

    Fuhrman, Joshua; Geller, Aaron M.; Rodriguez, Carl L.; Rasio, Frederic A.

    2017-01-01

    The recent detection of ripples in space-time by the Laser Interferometer Gravitational-wave Observatory (LIGO) has ushered in the age of gravitational wave astronomy. Binary black hole systems formed in the center of modest star clusters offer a possible gravitational wave source detectable by the LIGO or Laser Interferometer Space Antennae (LISA) collaborations. We simulate clusters containing 1-40K objects using direct integration from a customized version of NBODY6++GPU. We identify Binary Black Hole (BBH) objects of interest by an inspiral time sufficiently less than the age of the universe such that their coalescence might be detectable. Such objects are tracked through time within our N-body simulations to characterize the role of dynamics in the evolution of the BBH system using member exchanges and large orbital eccentricity changes as indicators of dynamic’s influence. We produce 41 BBH system candidates for detection by LIGO, all of which are dynamically formed. We observe several trends in the production of these potential BBH LIGO sources: a low-N cutoff in initial cluster size between 1-5K objects, high eccentricity oscillations, and the frequent formation of stable triple systems with the BBH as the inner binary.

  11. IoT Service Clustering for Dynamic Service Matchmaking.

    Science.gov (United States)

    Zhao, Shuai; Yu, Le; Cheng, Bo; Chen, Junliang

    2017-07-27

    As the adoption of service-oriented paradigms in the IoT (Internet of Things) environment, real-world devices will open their capabilities through service interfaces, which enable other functional entities to interact with them. In an IoT application, it is indispensable to find suitable services for satisfying users' requirements or replacing the unavailable services. However, from the perspective of performance, it is inappropriate to find desired services from the service repository online directly. Instead, clustering services offline according to their similarity and matchmaking or discovering service online in limited clusters is necessary. This paper proposes a multidimensional model-based approach to measure the similarity between IoT services. Then, density-peaks-based clustering is employed to gather similar services together according to the result of similarity measurement. Based on the service clustering, the algorithms of dynamic service matchmaking, discovery, and replacement will be performed efficiently. Evaluating experiments are conducted to validate the performance of proposed approaches, and the results are promising.

  12. Population dynamics and distribution of hydrocarbon utilizing ...

    African Journals Online (AJOL)

    Laboratory studies were carried out to assess the bacterial population dynamics and distribution in composite soil samples collected from five (5) different automobile workshops at various locations (Ikpa road, Nwaniba road, Udi street, Idakokpo lane and Mechanic village) within Uyo metropolis. The hydrocarbon utilizing ...

  13. Dynamics of proteasome distribution in living cells

    NARCIS (Netherlands)

    Reits, E. A.; Benham, A. M.; Plougastel, B.; Neefjes, J.; Trowsdale, J.

    1997-01-01

    Proteasomes are proteolytic complexes involved in non-lysosomal degradation which are localized in both the cytoplasm and the nucleus. The dynamics of proteasomes in living cells is unclear, as is their targeting to proteins destined for degradation. To investigate the intracellular distribution and

  14. Fragmentation dynamics of complex molecules and their clusters

    Science.gov (United States)

    Maclot, S.; Capron, M.; Maisonny, R.; Lawicki, A.; Chesnel, J.-Y.; Domaracka, A.; Méry, A.; Poully, J.-C.; Rangama, J.; Holm, A. I. S.; Johansson, H. A. B.; Seitz, F.; Rosen, S.; Schmidt, H.; Zettergren, H.; Rousseau, P.; Cederquist, H.; Huber, B. A.; Adoui, L.

    2013-04-01

    Complex molecular systems such as large molecules or clusters are characterised by a large number of degrees of freedom. Energies well in excess of individual thresholds for fragmentation can be stored for long times and metastable excited states become important. We will concentrate in this paper on the study of the response of such nanoscale systems, i.e. we will study excitation and fragmentation mechanisms induced by highly charged ion radiation, reflecting dynamic energy and charge flow processes. We will illustrate these relaxation processes for different molecular systems from Polycyclic Aromatic Hydrocarbons, water or biomolecule targets and their clusters in collision with multiply charged ions. We will emphasize that slow multiply charged ions provide an efficient way to study the stability of complex systems. Indeed, such ions are known to remove several electrons at large impact parameters resulting in a fast and gentle ionization.

  15. Molecular dynamics simulation of gold cluster growth during sputter deposition

    Energy Technology Data Exchange (ETDEWEB)

    Abraham, J. W., E-mail: abraham@theo-physik.uni-kiel.de; Bonitz, M., E-mail: bonitz@theo-physik.uni-kiel.de [Institut für Theoretische Physik und Astrophysik, Christian-Albrechts-Universität zu Kiel, Leibnizstraße 15, D-24098 Kiel (Germany); Strunskus, T.; Faupel, F. [Institut für Materialwissenschaft, Lehrstuhl für Materialverbunde, Christian-Albrechts-Universität zu Kiel, Kaiserstraße 2, D-24143 Kiel (Germany)

    2016-05-14

    We present a molecular dynamics simulation scheme that we apply to study the time evolution of the self-organized growth process of metal cluster assemblies formed by sputter-deposited gold atoms on a planar surface. The simulation model incorporates the characteristics of the plasma-assisted deposition process and allows for an investigation over a wide range of deposition parameters. It is used to obtain data for the cluster properties which can directly be compared with recently published experimental data for gold on polystyrene [M. Schwartzkopf et al., ACS Appl. Mater. Interfaces 7, 13547 (2015)]. While good agreement is found between the two, the simulations additionally provide valuable time-dependent real-space data of the surface morphology, some of whose details are hidden in the reciprocal-space scattering images that were used for the experimental analysis.

  16. Decomposition Patterns of Three C20 Isomer Clusters: Tight-binding Molecular Dynamics Simulation

    International Nuclear Information System (INIS)

    Lee, Changhoon; Lee, Kee Hag

    2016-01-01

    We investigated the decomposition pattern of three C 20 carbon isomer clusters using molecular dynamics simulations combined with the empirical tight-binding total energy calculation method. Here, the thermodynamic behaviors show up for 2 ps. Dynamic behavior is researched by considering the change in assembly energy, bond distance distribution, total energy, and potential energy as a function of temperature. The bonds start breaking around 3300, 4500, and 5100 K for cage, bowl, and ring isomers, respectively. Once a bond is broken, strain accumulates on the neighbors of that atom, and bond cleavage is further accelerated at the neighboring atoms. Based on the snapshots of decomposition, we suggest a C 20 formation scenario from linear carbon clusters to ring, bowl, or cage isomers.

  17. Dynamics of gravitational systems: Globular clusters and dark matter halos

    International Nuclear Information System (INIS)

    Oh, K.

    1989-01-01

    The evolution of globular clusters is investigated using a combination of the modified Fokker-Plank equation and numerical integrations of N-body systems. The orbit-averaged diffusion coefficients in the inner region of the cluster and integrated orbits of the stars in the outer region are used. The King-Michie distribution is adopted as an initial model. Both isotropic and anisotropic cases are examined. The following was found. There is no orbital phase dependence of tidal radius of clusters in eccentric orbits. The number of stars with retrograde orbits is similar to the number with prograde orbits inside the tidal radius for the isotropic case. Escape rates are similar to those found in previous work for the isotropic case but considerably smaller in the anisotropic case. Disk shocking is very efficient isotropizing the orbits of stars in the outer region of the cluster in the anisotropic case. The response of dark matter galactic halos during the dissipational collapse of the baryonic matter are investigated. N-body simulations are used with the total mass and z-component of angular momentum conserved. Then the baryonic matter is forced to contract, forming the final luminous components of the galaxy. Both slow and fast growth of the luminous components are considered. Relatively flat rotation curves are easily obtained for reasonable values of the free parameters. There is no significant difference between slow collapse and fast collapse for all these results

  18. Roles of dynamical symmetry breaking in driving oblate-prolate transitions of atomic clusters

    Energy Technology Data Exchange (ETDEWEB)

    Oka, Yurie, E-mail: ok-yu@fuji.waseda.jp; Yanao, Tomohiro, E-mail: yanao@waseda.jp [Department of Applied Mechanics and Aerospace Engineering, Waseda University, Tokyo 169-8555 (Japan); Koon, Wang Sang, E-mail: koon@cds.caltech.edu [Control and Dynamical Systems, California Institute of Technology, Pasadena, California 91125 (United States)

    2015-04-07

    This paper explores the driving mechanisms for structural transitions of atomic clusters between oblate and prolate isomers. We employ the hyperspherical coordinates to investigate structural dynamics of a seven-atom cluster at a coarse-grained level in terms of the dynamics of three gyration radii and three principal axes, which characterize overall mass distributions of the cluster. Dynamics of gyration radii is governed by two kinds of forces. One is the potential force originating from the interactions between atoms. The other is the dynamical forces called the internal centrifugal forces, which originate from twisting and shearing motions of the system. The internal centrifugal force arising from twisting motions has an effect of breaking the symmetry between two gyration radii. As a result, in an oblate isomer, activation of the internal centrifugal force that has the effect of breaking the symmetry between the two largest gyration radii is crucial in triggering structural transitions into prolate isomers. In a prolate isomer, on the other hand, activation of the internal centrifugal force that has the effect of breaking the symmetry between the two smallest gyration radii is crucial in triggering structural transitions into oblate isomers. Activation of a twisting motion that switches the movement patterns of three principal axes is also important for the onset of structural transitions between oblate and prolate isomers. Based on these trigger mechanisms, we finally show that selective activations of specific gyration radii and twisting motions, depending on the isomer of the cluster, can effectively induce structural transitions of the cluster. The results presented here could provide further insights into the control of molecular reactions.

  19. Roles of dynamical symmetry breaking in driving oblate-prolate transitions of atomic clusters

    Science.gov (United States)

    Oka, Yurie; Yanao, Tomohiro; Koon, Wang Sang

    2015-04-01

    This paper explores the driving mechanisms for structural transitions of atomic clusters between oblate and prolate isomers. We employ the hyperspherical coordinates to investigate structural dynamics of a seven-atom cluster at a coarse-grained level in terms of the dynamics of three gyration radii and three principal axes, which characterize overall mass distributions of the cluster. Dynamics of gyration radii is governed by two kinds of forces. One is the potential force originating from the interactions between atoms. The other is the dynamical forces called the internal centrifugal forces, which originate from twisting and shearing motions of the system. The internal centrifugal force arising from twisting motions has an effect of breaking the symmetry between two gyration radii. As a result, in an oblate isomer, activation of the internal centrifugal force that has the effect of breaking the symmetry between the two largest gyration radii is crucial in triggering structural transitions into prolate isomers. In a prolate isomer, on the other hand, activation of the internal centrifugal force that has the effect of breaking the symmetry between the two smallest gyration radii is crucial in triggering structural transitions into oblate isomers. Activation of a twisting motion that switches the movement patterns of three principal axes is also important for the onset of structural transitions between oblate and prolate isomers. Based on these trigger mechanisms, we finally show that selective activations of specific gyration radii and twisting motions, depending on the isomer of the cluster, can effectively induce structural transitions of the cluster. The results presented here could provide further insights into the control of molecular reactions.

  20. Roles of dynamical symmetry breaking in driving oblate-prolate transitions of atomic clusters

    International Nuclear Information System (INIS)

    Oka, Yurie; Yanao, Tomohiro; Koon, Wang Sang

    2015-01-01

    This paper explores the driving mechanisms for structural transitions of atomic clusters between oblate and prolate isomers. We employ the hyperspherical coordinates to investigate structural dynamics of a seven-atom cluster at a coarse-grained level in terms of the dynamics of three gyration radii and three principal axes, which characterize overall mass distributions of the cluster. Dynamics of gyration radii is governed by two kinds of forces. One is the potential force originating from the interactions between atoms. The other is the dynamical forces called the internal centrifugal forces, which originate from twisting and shearing motions of the system. The internal centrifugal force arising from twisting motions has an effect of breaking the symmetry between two gyration radii. As a result, in an oblate isomer, activation of the internal centrifugal force that has the effect of breaking the symmetry between the two largest gyration radii is crucial in triggering structural transitions into prolate isomers. In a prolate isomer, on the other hand, activation of the internal centrifugal force that has the effect of breaking the symmetry between the two smallest gyration radii is crucial in triggering structural transitions into oblate isomers. Activation of a twisting motion that switches the movement patterns of three principal axes is also important for the onset of structural transitions between oblate and prolate isomers. Based on these trigger mechanisms, we finally show that selective activations of specific gyration radii and twisting motions, depending on the isomer of the cluster, can effectively induce structural transitions of the cluster. The results presented here could provide further insights into the control of molecular reactions

  1. Kinetic energy distributions of sputtered neutral aluminum clusters: Al--Al6

    International Nuclear Information System (INIS)

    Coon, S.R.; Calaway, W.F.; Pellin, M.J.; Curlee, G.A.; White, J.M.

    1992-01-01

    Neutral aluminum clusters sputtered from polycrystalline aluminum were analyzed by laser postionization time-of-flight (TOF) mass spectrometry. The kinetic energy distributions of Al through Al 6 were measured by a neutrals time-of-flight technique. The interpretation of laser postionization TOF data to extract velocity and energy distributions is presented. The aluminum cluster distributions are qualitatively similar to previous copper cluster distribution measurements from our laboratory. In contrast to the steep high energy tails predicted by the single- or multiple- collision models, the measured cluster distributions have high energy power law dependences in the range of E -3 to E -4.5 . Correlated collision models may explain the substantial abundance of energetic clusters that are observed in these experiments. Possible influences of cluster fragmentation on the distributions are discussed

  2. Nickel-aluminum alloy clusters -- structural and dynamical properties

    Energy Technology Data Exchange (ETDEWEB)

    Jellinek, J.; Krissinel, E.B. [Argonne National Lab., IL (United States). Chemistry Div.

    1997-08-01

    Structural and dynamical properties of mixed Ni{sub n}Al{sub m} alloy clusters mimicked by a many-body potential are studied computationally for all the possible compositions n and m such that n + m = 13. It is shown that the manifold of the usually very large number of the different possible structural forms can be systematized by introducing classes of structures corresponding to the same concentration of the components, geometry and type of the central atom. General definitions of mixing energy and mixing coefficient are introduced, and it is shown that the energy ordering of the structural forms within each class is governed by the mixing coefficient. The peculiarities of the solid-to-liquid-like transition are described as a function of the concentration of the two types of atoms. These peculiarities are correlated with and explained in terms of the energy spectra of the structural forms. Class-dependent features of the dynamics are described and analyzed.

  3. A tight relation between the age distributions of stellar clusters and the properties of the interstellar medium in the host galaxy

    Science.gov (United States)

    Miholics, Meghan; Kruijssen, J. M. Diederik; Sills, Alison

    2017-09-01

    The age distributions of stellar cluster populations have long been proposed to probe the recent formation history of the host galaxy. However, progress is hampered by the limited understanding of cluster disruption by evaporation and tidal shocks. We study the age distributions of clusters in smoothed particle hydrodynamics simulations of isolated disc galaxies, which include a self-consistent, physical model for the formation and dynamical evolution of the cluster population and account for the variation of cluster disruption in time and space. We show that the downward slope of the cluster age distribution due to disruption cannot be reproduced with a single functional form, because the disruption rate exhibits systematic trends with cluster age (the 'cruel cradle effect'). This problem is resolved by using the median cluster age to trace cluster disruption. Across 120 independent galaxy snapshots and simulated cluster populations, we perform two-dimensional power-law fits of the median cluster age to various macroscopic physical quantities and find that it scales as t_med∝ Σ ^{-0.51± 0.03}σ _1D^{-0.85± 0.10}M_min^γ, for the gas surface density Σ, gas velocity dispersion σ1D, and minimum cluster mass Mmin. This scaling accurately describes observed cluster populations and indicates disruption by impulsive tidal shocks from the interstellar medium. The term M_min^γ provides a model-independent way to measure the mass dependence of the cluster disruption time γ. Finally, the ensemble-average cluster lifetime depends on the gas density less strongly than the instantaneous disruption time of single clusters. These results reflect the variation of cluster disruption in time and space. We provide quantitative ways of accounting for these physics in cluster population studies.

  4. Visualizing dynamical neural assemblies with a fuzzy synchronization clustering analysis.

    Science.gov (United States)

    Zhou, Shu; Wu, Yan; Dos Santos, Claudia C

    2009-12-01

    Phase synchrony has been proposed as a possible communication mechanism between cerebral regions. The participation index method (PIM) may be used to investigate integrating structures within an oscillatory network, based on the eigenvalue decomposition of matrix of bivariate synchronization indices. However, eigenvector orthogonality between clusters may result in categorization difficulties for hub oscillators and pseudoclustering phenomenon. Here, we propose a method of fuzzy synchronization clustering analysis (FSCA) to avoid the constraint of orthogonality by combining the fuzzy c-means algorithm with the phase-locking value. Following mathematical derivation, we cross-validated the FSCA and the PIM using the same multichannel phase time series of event-related EEG from a subject performing a working memory task. Both clustering methods produced consistent findings for the qualitatively salient configuration of the original network-illustrated here by a visualization technique. In contrast to PIM, use of common virtual oscillatory centroids enabled the FSCA to reveal multiple dynamical neural assemblies as well as the unitary phase information within each assembly.

  5. Beyond clustering: mean-field dynamics on networks with arbitrary subgraph composition.

    Science.gov (United States)

    Ritchie, Martin; Berthouze, Luc; Kiss, Istvan Z

    2016-01-01

    Clustering is the propensity of nodes that share a common neighbour to be connected. It is ubiquitous in many networks but poses many modelling challenges. Clustering typically manifests itself by a higher than expected frequency of triangles, and this has led to the principle of constructing networks from such building blocks. This approach has been generalised to networks being constructed from a set of more exotic subgraphs. As long as these are fully connected, it is then possible to derive mean-field models that approximate epidemic dynamics well. However, there are virtually no results for non-fully connected subgraphs. In this paper, we provide a general and automated approach to deriving a set of ordinary differential equations, or mean-field model, that describes, to a high degree of accuracy, the expected values of system-level quantities, such as the prevalence of infection. Our approach offers a previously unattainable degree of control over the arrangement of subgraphs and network characteristics such as classical node degree, variance and clustering. The combination of these features makes it possible to generate families of networks with different subgraph compositions while keeping classical network metrics constant. Using our approach, we show that higher-order structure realised either through the introduction of loops of different sizes or by generating networks based on different subgraphs but with identical degree distribution and clustering, leads to non-negligible differences in epidemic dynamics.

  6. HOW SIGNIFICANT IS RADIATION PRESSURE IN THE DYNAMICS OF THE GAS AROUND YOUNG STELLAR CLUSTERS?

    Energy Technology Data Exchange (ETDEWEB)

    Silich, Sergiy; Tenorio-Tagle, Guillermo, E-mail: silich@inaoep.mx [Instituto Nacional de Astrofisica Optica y Electronica, AP 51, 72000 Puebla (Mexico)

    2013-03-01

    The impact of radiation pressure on the dynamics of the gas in the vicinity of young stellar clusters is thoroughly discussed. The radiation over the thermal/ram pressure ratio time evolution is calculated explicitly and the crucial roles of the cluster mechanical power, the strong time evolution of the ionizing photon flux, and the bolometric luminosity of the exciting cluster are stressed. It is shown that radiation has only a narrow window of opportunity to dominate the wind-driven shell dynamics. This may occur only at early stages of the bubble evolution and if the shell expands into a dusty and/or a very dense proto-cluster medium. The impact of radiation pressure on the wind-driven shell always becomes negligible after about 3 Myr. Finally, the wind-driven model results allow one to compare the model predictions with the distribution of thermal pressure derived from X-ray observations. The shape of the thermal pressure profile then allows us to distinguish between the energy and the momentum-dominated regimes of expansion and thus conclude whether radiative losses of energy or the leakage of hot gas from the bubble interior have been significant during bubble evolution.

  7. Dynamic integration of remote cloud resources into local computing clusters

    Energy Technology Data Exchange (ETDEWEB)

    Fleig, Georg; Erli, Guenther; Giffels, Manuel; Hauth, Thomas; Quast, Guenter; Schnepf, Matthias [Institut fuer Experimentelle Kernphysik, Karlsruher Institut fuer Technologie (Germany)

    2016-07-01

    In modern high-energy physics (HEP) experiments enormous amounts of data are analyzed and simulated. Traditionally dedicated HEP computing centers are built or extended to meet this steadily increasing demand for computing resources. Nowadays it is more reasonable and more flexible to utilize computing power at remote data centers providing regular cloud services to users as they can be operated in a more efficient manner. This approach uses virtualization and allows the HEP community to run virtual machines containing a dedicated operating system and transparent access to the required software stack on almost any cloud site. The dynamic management of virtual machines depending on the demand for computing power is essential for cost efficient operation and sharing of resources with other communities. For this purpose the EKP developed the on-demand cloud manager ROCED for dynamic instantiation and integration of virtualized worker nodes into the institute's computing cluster. This contribution will report on the concept of our cloud manager and the implementation utilizing a remote OpenStack cloud site and a shared HPC center (bwForCluster located in Freiburg).

  8. Connecting micro dynamics and population distributions in system dynamics models.

    Science.gov (United States)

    Fallah-Fini, Saeideh; Rahmandad, Hazhir; Chen, Hsin-Jen; Xue, Hong; Wang, Youfa

    2013-01-01

    Researchers use system dynamics models to capture the mean behavior of groups of indistinguishable population elements (e.g., people) aggregated in stock variables. Yet, many modeling problems require capturing the heterogeneity across elements with respect to some attribute(s) (e.g., body weight). This paper presents a new method to connect the micro-level dynamics associated with elements in a population with the macro-level population distribution along an attribute of interest without the need to explicitly model every element. We apply the proposed method to model the distribution of Body Mass Index and its changes over time in a sample population of American women obtained from the U.S. National Health and Nutrition Examination Survey. Comparing the results with those obtained from an individual-based model that captures the same phenomena shows that our proposed method delivers accurate results with less computation than the individual-based model.

  9. Connecting micro dynamics and population distributions in system dynamics models

    Science.gov (United States)

    Rahmandad, Hazhir; Chen, Hsin-Jen; Xue, Hong; Wang, Youfa

    2014-01-01

    Researchers use system dynamics models to capture the mean behavior of groups of indistinguishable population elements (e.g., people) aggregated in stock variables. Yet, many modeling problems require capturing the heterogeneity across elements with respect to some attribute(s) (e.g., body weight). This paper presents a new method to connect the micro-level dynamics associated with elements in a population with the macro-level population distribution along an attribute of interest without the need to explicitly model every element. We apply the proposed method to model the distribution of Body Mass Index and its changes over time in a sample population of American women obtained from the U.S. National Health and Nutrition Examination Survey. Comparing the results with those obtained from an individual-based model that captures the same phenomena shows that our proposed method delivers accurate results with less computation than the individual-based model. PMID:25620842

  10. Catching Galactic open clusters in advanced stages of dynamical evolution

    Science.gov (United States)

    Angelo, M. S.; Piatti, A. E.; Dias, W. S.; Maia, F. F. S.

    2018-04-01

    During their dynamical evolution, Galactic open clusters (OCs) gradually lose their stellar content mainly because of internal relaxation and tidal forces. In this context, the study of dynamically evolved OCs is necessary to properly understand such processes. We present a comprehensive Washington CT1 photometric analysis of six sparse OCs, namely: ESO 518-3, Ruprecht 121, ESO 134-12, NGC 6573, ESO 260-7 and ESO 065-7. We employed Markov chain Monte-Carlo simulations to robustly determine the central coordinates and the structural parameters and T1 × (C - T1) colour-magnitude diagrams (CMDs) cleaned from field contamination were used to derive the fundamental parameters. ESO 518-03, Ruprecht 121, ESO 134-12 and NGC 6573 resulted to be of nearly the same young age (8.2 ≤log(t yr-1) ≤ 8.3); ESO 260-7 and ESO065-7 are of intermediate age (9.2 ≤log(t yr-1) ≤ 9.4). All studied OCs are located at similar Galactocentric distances (RG ˜ 6 - 6.9 kpc), considering uncertainties, except for ESO 260-7 (RG = 8.9 kpc). These OCs are in a tidally filled regime and are dynamically evolved, since they are much older than their half-mass relaxation times (t/trh ≳ 30) and present signals of low-mass star depletion. We distinguished two groups: those dynamically evolving towards final disruptions and those in an advanced dynamical evolutionary stage. Although we do not rule out that the Milky Way potential could have made differentially faster their dynamical evolutions, we speculate here with the possibility that they have been mainly driven by initial formation conditions.

  11. Dynamical Model of Fission Fragment Angular Distribution

    Science.gov (United States)

    Drozdov, V. A.; Eremenko, D. O.; Fotina, O. V.; Platonov, S. Yu.; Yuminov, O. A.; Giardina, G.; Taccone, A.

    2002-01-01

    A dynamical model of fission fragment angular distributions is suggested. The model allows one to calculate fission fragment angular distributions, prescission light particle multyplicities, evaporation residue cross sections etc. for the cases of decay of hot and rotating heavy nuclei. The experimental data on angular anisotropies of fission fragments and prescission neutron multiplicities are analyzed for the 16O + 208Pb, 232Th, 248Cm and 238U reactions at the energies of the incident 16O ions ranging from 90 to 160 MeV. This analysis allows us to extract both the nuclear friction coefficient value and the relaxation time for the tilting mode. It is also demonstrated that the angular distributions are sensitive to the deformation dependence of the nuclear friction.

  12. Structures and dynamical properties of Cn, Sin, Gen, and Snn clusters with n up to 13

    International Nuclear Information System (INIS)

    Lu, Zhong-Yi; Wang, Cai-Zhuang; Ho, Kai-Ming

    2000-01-01

    Car-Parrinello molecular dynamics simulated annealings were carried out for clusters Si n , Ge n , and Sn n (n≤13). We investigate the temperature regions in which these clusters transform from a ''liquidlike'' phase to a ''solidlike'' phase, and then from the ''solidlike'' phase to the ground-state structures. Additional simulated annealing was also performed for the cluster C 13 which is selected as a prototype of small carbon clusters. In addition to the discovery of structures for Sn and Ge clusters, our simulation results also provide insights into the dynamics of cluster formation. (c) 2000 The American Physical Society

  13. K-means clustering versus validation measures: a data-distribution perspective.

    Science.gov (United States)

    Xiong, Hui; Wu, Junjie; Chen, Jian

    2009-04-01

    K-means is a well-known and widely used partitional clustering method. While there are considerable research efforts to characterize the key features of the K-means clustering algorithm, further investigation is needed to understand how data distributions can have impact on the performance of K-means clustering. To that end, in this paper, we provide a formal and organized study of the effect of skewed data distributions on K-means clustering. Along this line, we first formally illustrate that K-means tends to produce clusters of relatively uniform size, even if input data have varied "true" cluster sizes. In addition, we show that some clustering validation measures, such as the entropy measure, may not capture this uniform effect and provide misleading information on the clustering performance. Viewed in this light, we provide the coefficient of variation (CV) as a necessary criterion to validate the clustering results. Our findings reveal that K-means tends to produce clusters in which the variations of cluster sizes, as measured by CV, are in a range of about 0.3-1.0. Specifically, for data sets with large variation in "true" cluster sizes (e.g., CV > 1.0), K-means reduces variation in resultant cluster sizes to less than 1.0. In contrast, for data sets with small variation in "true" cluster sizes (e.g., CV K-means increases variation in resultant cluster sizes to greater than 0.3. In other words, for the earlier two cases, K-means produces the clustering results which are away from the "true" cluster distributions.

  14. Dissipation and energy balance in electronic dynamics of Na clusters

    Science.gov (United States)

    Vincendon, Marc; Suraud, Eric; Reinhard, Paul-Gerhard

    2017-06-01

    We investigate the impact of dissipation on the energy balance in the electron dynamics of metal clusters excited by strong electro-magnetic pulses. The dynamics is described theoretically by Time-Dependent Density-Functional Theory (TDDFT) at the level of Local Density Approximation (LDA) augmented by a self interaction correction term and a quantum collision term in Relaxation-Time Approximation (RTA). We evaluate the separate contributions to the total excitation energy, namely energy exported by electron emission, potential energy due to changing charge state, intrinsic kinetic and potential energy, and collective flow energy. The balance of these energies is studied as function of the laser parameters (frequency, intensity, pulse length) and as function of system size and charge. We also look at collisions with a highly charged ion and here at the dependence on the impact parameter (close versus distant collisions). Dissipation turns out to be small where direct electron emission prevails namely for laser frequencies above any ionization threshold and for slow electron extraction in distant collisions. Dissipation is large for fast collisions and at low laser frequencies, particularly at resonances. Contribution to the Topical Issue "Dynamics of Systems at the Nanoscale", edited by Andrey Solov'yov and Andrei Korol.

  15. Functional clustering in hippocampal cultures: relating network structure and dynamics

    International Nuclear Information System (INIS)

    Feldt, S; Dzakpasu, R; Olariu, E; Żochowski, M; Wang, J X; Shtrahman, E

    2010-01-01

    In this work we investigate the relationship between gross anatomic structural network properties, neuronal dynamics and the resultant functional structure in dissociated rat hippocampal cultures. Specifically, we studied cultures as they developed under two conditions: the first supporting glial cell growth (high glial group), and the second one inhibiting it (low glial group). We then compared structural network properties and the spatio-temporal activity patterns of the neurons. Differences in dynamics between the two groups could be linked to the impact of the glial network on the neuronal network as the cultures developed. We also implemented a recently developed algorithm called the functional clustering algorithm (FCA) to obtain the resulting functional network structure. We show that this new algorithm is useful for capturing changes in functional network structure as the networks evolve over time. The FCA detects changes in functional structure that are consistent with expected dynamical differences due to the impact of the glial network. Cultures in the high glial group show an increase in global synchronization as the cultures age, while those in the low glial group remain locally synchronized. We additionally use the FCA to quantify the amount of synchronization present in the cultures and show that the total level of synchronization in the high glial group is stronger than in the low glial group. These results indicate an interdependence between the glial and neuronal networks present in dissociated cultures

  16. Dynamic configuration of the CMS Data Acquisition cluster

    CERN Document Server

    Bauer, Gerry; Biery, Kurt; Boyer, Vincent; Branson, James; Cano, Eric; Cheung, Harry; Ciganek, Marek; Cittolin, Sergio; Coarasa, Jose Antonio; Deldicque, Christian; Dusinberre, Elizabeth; Erhan, Samim; Fortes Rodrigues, Fabiana; Gigi, Dominique; Glege, Frank; Gomez-Reino, Robert; Gutleber, Johannes; Hatton, Derek; Laurens, Jean-Francois; Lopez Perez, Juan Antonio; Meijers, Frans; Meschi, Emilio; Meyer, Andreas; Mommsen, Remigius K; Moser, Roland; O'Dell, Vivian; Oh, Alexander; Orsini, Luciano; Patras, Vaios; Paus, Christoph; Petrucci, Andrea; Pieri, Marco; Racz, Attila; Sakulin, Hannes; Sani, Matteo; Schieferdecker, Philipp; Schwick, Christoph; Shpakov, Dennis; Simon, Sean; Sumorok, Konstanty; Zanetti, Marco

    2010-01-01

    The CMS Data Acquisition cluster, which runs around 10000 applications, is configured dynamically at run time. XML configuration documents determine what applications are executed on each node and over what networks these applications communicate. Through this mechanism the DAQ System may be adapted to the required performance, partitioned in order to perform (test-) runs in parallel, or re-structured in case of hardware faults. This paper presents the CMS DAQ Configurator tool, which is used to generate comprehensive configurations of the CMS DAQ system based on a high-level description given by the user. Using a database of configuration templates and a database containing a detailed model of hardware modules, data and control links, nodes and the network topology, the tool automatically determines which applications are needed, on which nodes they should run, and over which networks the event traffic will flow. The tool computes application parameters and generates the XML configuration documents as well a...

  17. Communication: Diverse nanoscale cluster dynamics: Diffusion of 2D epitaxial clusters

    Science.gov (United States)

    Lai, King C.; Evans, James W.; Liu, Da-Jiang

    2017-11-01

    The dynamics of nanoscale clusters can be distinct from macroscale behavior described by continuum formalisms. For diffusion of 2D clusters of N atoms in homoepitaxial systems mediated by edge atom hopping, macroscale theory predicts simple monotonic size scaling of the diffusion coefficient, DN ˜ N-β, with β = 3/2. However, modeling for nanoclusters on metal(100) surfaces reveals that slow nucleation-mediated diffusion displaying weak size scaling β < 1 occurs for "perfect" sizes Np = L2 and L(L+1) for integer L = 3,4,… (with unique square or near-square ground state shapes), and also for Np+3, Np+4,…. In contrast, fast facile nucleation-free diffusion displaying strong size scaling β ≈ 2.5 occurs for sizes Np+1 and Np+2. DN versus N oscillates strongly between the slowest branch (for Np+3) and the fastest branch (for Np+1). All branches merge for N = O(102), but macroscale behavior is only achieved for much larger N = O(103). This analysis reveals the unprecedented diversity of behavior on the nanoscale.

  18. Membership and Dynamical Parameters of the Open Cluster NGC 1039

    Science.gov (United States)

    Wang, Jiaxin; Ma, Jun; Wu, Zhenyu; Zhou, Xu

    2017-11-01

    In this paper, we analyze the open cluster NGC 1039. This young open cluster is observed as a part of Beijing-Arizona-Taiwan-Connecticut Multicolor Sky Survey. Combining our observations with the Sloan Digital Sky Survey photometric data, we employ the Padova stellar model and the zero-age main-sequence curve to the data to derive a reddening, E(B-V)=0.10+/- 0.02, and a distance modulus, {(m-M)}0=8.4+/- 0.2, for NGC 1039. The photometric membership probabilities of stars in the region of NGC 1039 are derived using the spectral energy distribution-fitting method. According to the membership probabilities ({P}{SED}) obtained here, 582 stars are cluster members with {P}{SED} larger than 60%. In addition, we determine the structural parameters of NGC 1039 by fitting its radial density profile with the King model. These parameters are a core radius, {R}{{c}}=4.44+/- 1.31 {pc}; a tidal radius, {R}{{t}}=13.57+/- 4.85 {pc}; and a concentration parameter of {C}0={log}({R}{{t}}/{R}{{c}})=0.49+/- 0.20. We also fit the observed mass function of NGC 1039 with masses from 0.3 {M}⊙ to 1.65 {M}⊙ with a power-law function {{Φ }}(m)\\propto {m}α to derive its slopes of mass functions of different spatial regions. The results obtained here show that the slope of the mass function of NGC 1039 is flatter in the central regions (α = 0.117), becomes steeper at larger radii (α = -2.878), and breaks at {m}{break}≈ 0.80 {M}⊙ . In particular, for the first time, our results show that the mass segregation appears in NGC 1039.

  19. Cardea: Dynamic Access Control in Distributed Systems

    Science.gov (United States)

    Lepro, Rebekah

    2004-01-01

    Modern authorization systems span domains of administration, rely on many different authentication sources, and manage complex attributes as part of the authorization process. This . paper presents Cardea, a distributed system that facilitates dynamic access control, as a valuable piece of an inter-operable authorization framework. First, the authorization model employed in Cardea and its functionality goals are examined. Next, critical features of the system architecture and its handling of the authorization process are then examined. Then the S A M L and XACML standards, as incorporated into the system, are analyzed. Finally, the future directions of this project are outlined and connection points with general components of an authorization system are highlighted.

  20. The Hierarchical Distribution of the Young Stellar Clusters in Six Local Star-forming Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Grasha, K.; Calzetti, D. [Astronomy Department, University of Massachusetts, Amherst, MA 01003 (United States); Adamo, A.; Messa, M. [Dept. of Astronomy, The Oskar Klein Centre, Stockholm University, Stockholm (Sweden); Kim, H. [Gemini Observatory, La Serena (Chile); Elmegreen, B. G. [IBM Research Division, T.J. Watson Research Center, Yorktown Hts., NY (United States); Gouliermis, D. A. [Zentrum für Astronomie der Universität Heidelberg, Institut für Theoretische Astrophysik, Albert-Ueberle-Str. 2, D-69120 Heidelberg (Germany); Dale, D. A. [Dept. of Physics and Astronomy, University of Wyoming, Laramie, WY (United States); Fumagalli, M. [Institute for Computational Cosmology and Centre for Extragalactic Astronomy, Durham University, Durham (United Kingdom); Grebel, E. K.; Shabani, F. [Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, D-69120 Heidelberg (Germany); Johnson, K. E. [Dept. of Astronomy, University of Virginia, Charlottesville, VA (United States); Kahre, L. [Dept. of Astronomy, New Mexico State University, Las Cruces, NM (United States); Kennicutt, R. C. [Institute of Astronomy, University of Cambridge, Cambridge (United Kingdom); Pellerin, A. [Dept. of Physics and Astronomy, State University of New York at Geneseo, Geneseo NY (United States); Ryon, J. E.; Ubeda, L. [Space Telescope Science Institute, Baltimore, MD (United States); Smith, L. J. [European Space Agency/Space Telescope Science Institute, Baltimore, MD (United States); Thilker, D., E-mail: kgrasha@astro.umass.edu [Dept. of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD (United States)

    2017-05-10

    We present a study of the hierarchical clustering of the young stellar clusters in six local (3–15 Mpc) star-forming galaxies using Hubble Space Telescope broadband WFC3/UVIS UV and optical images from the Treasury Program LEGUS (Legacy ExtraGalactic UV Survey). We identified 3685 likely clusters and associations, each visually classified by their morphology, and we use the angular two-point correlation function to study the clustering of these stellar systems. We find that the spatial distribution of the young clusters and associations are clustered with respect to each other, forming large, unbound hierarchical star-forming complexes that are in general very young. The strength of the clustering decreases with increasing age of the star clusters and stellar associations, becoming more homogeneously distributed after ∼40–60 Myr and on scales larger than a few hundred parsecs. In all galaxies, the associations exhibit a global behavior that is distinct and more strongly correlated from compact clusters. Thus, populations of clusters are more evolved than associations in terms of their spatial distribution, traveling significantly from their birth site within a few tens of Myr, whereas associations show evidence of disruption occurring very quickly after their formation. The clustering of the stellar systems resembles that of a turbulent interstellar medium that drives the star formation process, correlating the components in unbound star-forming complexes in a hierarchical manner, dispersing shortly after formation, suggestive of a single, continuous mode of star formation across all galaxies.

  1. Parallel Hyperspectral Image Processing on Distributed Multi-Cluster Systems

    NARCIS (Netherlands)

    Liu, F.; Seinstra, F.J.; Plaza, A.J.

    2011-01-01

    Computationally efficient processing of hyperspectral image cubes can be greatly beneficial in many application domains, including environmental modeling, risk/hazard prevention and response, and defense/security. As individual cluster computers often cannot satisfy the computational demands of

  2. Mass spectrometric probes of metal cluster distributions and metastable ion decay

    International Nuclear Information System (INIS)

    Parks, E.K.; Liu, K.; Cole, S.K.; Riley, S.J.

    1988-01-01

    The study of metal clusters has provided both an opportunity and a challenge to the application of mass spectrometry. These days the most often-used technique for cluster generation - laser vaporization - leads to extensive distributions of cluster sizes, from one to perhaps thousands of atoms, and most studies reported to date use excimer laser ionization and time-of-flight mass spectrometry for cluster detection. Our apparatus is a simple one-stage TOF design employing Wiley-McLauren spatial focusing and a one-meter drift tube. In a second apparatus employing a pulsed valve in the cluster source, we see asymmetric broadening of niobium cluster mass peaks under multiphoton ionization conditions, indicating metastable decay of parent cluster ions. Other studies of niobium clusters have shown no such asymmetric peaks. 2 figs

  3. A Distributed Agent Implementation of Multiple Species Flocking Model for Document Partitioning Clustering

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Xiaohui [ORNL; Potok, Thomas E [ORNL

    2006-01-01

    The Flocking model, first proposed by Craig Reynolds, is one of the first bio-inspired computational collective behavior models that has many popular applications, such as animation. Our early research has resulted in a flock clustering algorithm that can achieve better performance than the Kmeans or the Ant clustering algorithms for data clustering. This algorithm generates a clustering of a given set of data through the embedding of the highdimensional data items on a two-dimensional grid for efficient clustering result retrieval and visualization. In this paper, we propose a bio-inspired clustering model, the Multiple Species Flocking clustering model (MSF), and present a distributed multi-agent MSF approach for document clustering.

  4. Agent-based method for distributed clustering of textual information

    Science.gov (United States)

    Potok, Thomas E [Oak Ridge, TN; Reed, Joel W [Knoxville, TN; Elmore, Mark T [Oak Ridge, TN; Treadwell, Jim N [Louisville, TN

    2010-09-28

    A computer method and system for storing, retrieving and displaying information has a multiplexing agent (20) that calculates a new document vector (25) for a new document (21) to be added to the system and transmits the new document vector (25) to master cluster agents (22) and cluster agents (23) for evaluation. These agents (22, 23) perform the evaluation and return values upstream to the multiplexing agent (20) based on the similarity of the document to documents stored under their control. The multiplexing agent (20) then sends the document (21) and the document vector (25) to the master cluster agent (22), which then forwards it to a cluster agent (23) or creates a new cluster agent (23) to manage the document (21). The system also searches for stored documents according to a search query having at least one term and identifying the documents found in the search, and displays the documents in a clustering display (80) of similarity so as to indicate similarity of the documents to each other.

  5. The Evolution of Galaxies Through the Spatial Distribution of Their Globular Clusters: the Brightest Galaxies in Fornax

    Science.gov (United States)

    Zegeye, David W.

    2018-01-01

    We present a study of the evolution of the 10 brightest galaxies in the Fornax Cluster, as reconstructed through their Globular Cluster (GC) populations. GCs can be characterized by their projected two-dimensional (2D) spatial distribution. Over- or under-densities in the GC distribution, can be linked to events in the host galaxy assembly history, and used to constrain the properties of their progenitors. With HST/ACS imaging, we identified significant structures in the GC distribution of the 10 galaxies investigated, with some of the galaxies possessing structures with >10-sigma significance. GC over-densities have been found within the galaxies, with significant differences between the red and blue GC population. For elongated galaxies, structures are preferentially to be aligned along the major axis. Fornax Cluster galaxies appear to be more dynamically relaxed than the Virgo Cluster galaxies previously investigated with the same methodology by D'Abrusco et al. (2016). However, from these observations, the evident imprints left in the spatial distribution of GCs in these galaxies suggest a similarly intense history of interactions.The SAO REU program is funded by the National Science Foundation REU and Department of Defense ASSURE programs under NSF Grant AST-1659473, and by the Smithsonian Institution.

  6. Cluster dynamics modelling of materials: A new hybrid deterministic/stochastic coupling approach

    Science.gov (United States)

    Terrier, Pierre; Athènes, Manuel; Jourdan, Thomas; Adjanor, Gilles; Stoltz, Gabriel

    2017-12-01

    Deterministic simulations of the rate equations governing cluster dynamics in materials are limited by the number of equations to integrate. Stochastic simulations are limited by the high frequency of certain events. We propose a coupling method combining deterministic and stochastic approaches. It allows handling different time scale phenomena for cluster dynamics. This method, based on a splitting of the dynamics, is generic and we highlight two different hybrid deterministic/stochastic methods. These coupling schemes are highly parallelizable and specifically designed to treat large size cluster problems. The proof of concept is made on a simple model of vacancy clustering under thermal ageing.

  7. Clustering Timber Harvests and the Effects of Dynamic Forest Management Policy on Forest Fragmentation

    Science.gov (United States)

    Eric J. Gustafson

    1998-01-01

    To integrate multiple uses (mature forest and commodity production) better on forested lands, timber management strategies that cluster harvests have been proposed. One such approach clusters harvest activity in space and time, and rotates timber production zones across the landscape with a long temporal period (dynamic zoning). Dynamic zoning has...

  8. Unconventional planetary orbits and dynamical interactions in stellar clusters

    Science.gov (United States)

    de la Fuente Marcos, R.; de la Fuente Marcos, C.

    In the last few years the search for planets around main sequence stars other than the Sun has experienced rapid progress but, far from clarifying our knowledge in the field of planet formation, the newly discovered planets have given rise to new uncertainties about our current paradigm for planetary system formation because none of them resemble our own solar system very closely. The unconventional properties of the confirmed extrasolar giant-planets include very small semi-major axes (0.04-0.05 AU) and highly eccentric (0.3-0.7) orbits. We show that some of the unusual features observed in extrasolar planetary systems, which can not be explained by the standard theories, may be a by-product of dynamical interactions between planetary systems and stars in clusters. In this research, the orbital modification problem is studied through the direct numerical integration of entire medium-rich open clusters (N = 1000) with the code NBODY5 (Aarseth 1985). For simplicity, the planetary systems studied in this work consist of only one giant planet and its host star. Our models also include a modern IMF, stellar evolution, and realistic values for the primordial binary fraction. The modification of the primordial orbital elements of planetary systems would be produced through formation of temporarily stable hierarchical systems. On the other hand, unstable configurations can eject one or more planets frm the system. In addition, physical collisions between stars and planets with very small semi-major axes and eccentric orbits may result in atypical stellar metallicities.

  9. Biophysical controls on cluster dynamics and architectural differentiation of microbial biofilms in contrasting flow environments

    Science.gov (United States)

    Hödl, Iris; Mari, Lorenzo; Bertuzzo, Enrico; Suweis, Samir; Besemer, Katharina; Rinaldo, Andrea; Battin, Tom J

    2014-01-01

    Ecology, with a traditional focus on plants and animals, seeks to understand the mechanisms underlying structure and dynamics of communities. In microbial ecology, the focus is changing from planktonic communities to attached biofilms that dominate microbial life in numerous systems. Therefore, interest in the structure and function of biofilms is on the rise. Biofilms can form reproducible physical structures (i.e. architecture) at the millimetre-scale, which are central to their functioning. However, the spatial dynamics of the clusters conferring physical structure to biofilms remains often elusive. By experimenting with complex microbial communities forming biofilms in contrasting hydrodynamic microenvironments in stream mesocosms, we show that morphogenesis results in ‘ripple-like’ and ‘star-like’ architectures – as they have also been reported from monospecies bacterial biofilms, for instance. To explore the potential contribution of demographic processes to these architectures, we propose a size-structured population model to simulate the dynamics of biofilm growth and cluster size distribution. Our findings establish that basic physical and demographic processes are key forces that shape apparently universal biofilm architectures as they occur in diverse microbial but also in single-species bacterial biofilms. PMID:23879839

  10. Internal velocity and mass distributions in simulated clusters of galaxies for a variety of cosmogonic models

    Science.gov (United States)

    Cen, Renyue

    1994-01-01

    The mass and velocity distributions in the outskirts (0.5-3.0/h Mpc) of simulated clusters of galaxies are examined for a suite of cosmogonic models (two Omega(sub 0) = 1 and two Omega(sub 0) = 0.2 models) utilizing large-scale particle-mesh (PM) simulations. Through a series of model computations, designed to isolate the different effects, we find that both Omega(sub 0) and P(sub k) (lambda less than or = 16/h Mpc) are important to the mass distributions in clusters of galaxies. There is a correlation between power, P(sub k), and density profiles of massive clusters; more power tends to point to the direction of a stronger correlation between alpha and M(r less than 1.5/h Mpc); i.e., massive clusters being relatively extended and small mass clusters being relatively concentrated. A lower Omega(sub 0) universe tends to produce relatively concentrated massive clusters and relatively extended small mass clusters compared to their counterparts in a higher Omega(sub 0) model with the same power. Models with little (initial) small-scale power, such as the hot dark matter (HDM) model, produce more extended mass distributions than the isothermal distribution for most of the mass clusters. But the cold dark matter (CDM) models show mass distributions of most of the clusters more concentrated than the isothermal distribution. X-ray and gravitational lensing observations are beginning providing useful information on the mass distribution in and around clusters; some interesting constraints on Omega(sub 0) and/or the (initial) power of the density fluctuations on scales lambda less than or = 16/h Mpc (where linear extrapolation is invalid) can be obtained when larger observational data sets, such as the Sloan Digital Sky Survey, become available.

  11. Dynamic PROOF clusters with PoD: architecture and user experience

    Science.gov (United States)

    Manafov, Anar

    2011-12-01

    PROOF on Demand (PoD) is a tool-set, which sets up a PROOF cluster on any resource management system. PoD is a user oriented product with an easy to use GUI and a command-line interface. It is fully automated. No administrative privileges or special knowledge is required to use it. PoD utilizes a plug-in system, to use different job submission front-ends. The current PoD distribution is shipped with LSF, Torque (PBS), Grid Engine, Condor, gLite, and SSH plug-ins. The product is to be extended. We therefore plan to implement a plug-in for AliEn Grid as well. Recently developed algorithms made it possible to efficiently maintain two types of connections: packet-forwarding and native PROOF connections. This helps to properly handle most kinds of workers, with and without firewalls. PoD maintains the PROOF environment automatically and, for example, prevents resource misusage in case when workers idle for too long. As PoD matures as a product and provides more plug-ins, it's used as a standard for setting up dynamic PROOF clusters in many different institutions. The GSI Analysis Facility (GSIAF) is in production since 2007. The static PROOF cluster has been phased out end of 2009. GSIAF is now completely based on PoD. Users create private dynamic PROOF clusters on the general purpose batch farm. This provides an easier resource sharing between interactive local batch and Grid usage. The main user communities are FAIR and ALICE.

  12. Dynamical difference between the cD galaxy and the diffuse, stellar component in simulated galaxy clusters

    Science.gov (United States)

    Dolag, K.; Murante, G.; Borgani, S.

    2010-07-01

    Member galaxies within galaxy clusters nowadays can be routinely identified in cosmological, hydrodynamical simulations using methods based on identifying self bound, locally over dense substructures. However, distinguishing the central galaxy from the stellar diffuse component within clusters is notoriously difficult, and in the centre it is not even clear if two distinct stellar populations exist. Here, after subtracting all member galaxies, we use the velocity distribution of the remaining stars and detect two dynamically, well-distinct stellar components within simulated galaxy clusters. These differences in the dynamics can be used to apply an unbinding procedure which leads to a spatial separation of the two components into a cD and a diffuse stellar component (DSC). Applying our new algorithm to a cosmological, hydrodynamical simulation we find that - in line with previous studies - these two components have clearly distinguished spatial and velocity distributions as well as different star formation histories. We show that the DSC fraction - which can broadly be associated with the observed intracluster light - does not depend on the virial mass of the galaxy cluster and is much more sensitive to the formation history of the cluster. We conclude that the separation of the cD and the DSC in simulations, based on our dynamical criteria, is more physically motivated than current methods which depend on implicit assumptions on a length-scale associated with the cD galaxy and therefore represent a step forward in understanding the different stellar components within galaxy clusters. Our results also show the importance of analysing the dynamics of the DSC to characterize its properties and understand its origin.

  13. A comparison of two mass distributions applicable to globular clusters and dwarf galaxies

    Directory of Open Access Journals (Sweden)

    Ninković Slobodan D.

    2004-01-01

    Full Text Available A particular case of mass distribution in stellar systems, already described in the literature, is compared to the King model of mass distribution. For the cases which would correspond to the description of real stellar systems such as the globular clusters and dwarf galaxies, one finds a satisfactory agreement between these two mass distributions.

  14. Cluster of CubeSats for Multi-Angle Measurements of Bidirectional Reflectance Distribution Function (BRDF)

    Data.gov (United States)

    National Aeronautics and Space Administration — Cluster of CubeSats for Multi-Angle Measurements of Bidirectional Reflectance Distribution Function (BRDF) The rapidly advancing capabilities of small satellite...

  15. Spatial and kinematic distributions of transition populations in intermediate redshift galaxy clusters

    International Nuclear Information System (INIS)

    Crawford, Steven M.; Wirth, Gregory D.; Bershady, Matthew A.

    2014-01-01

    We analyze the spatial and velocity distributions of confirmed members in five massive clusters of galaxies at intermediate redshift (0.5 < z < 0.9) to investigate the physical processes driving galaxy evolution. Based on spectral classifications derived from broad- and narrow-band photometry, we define four distinct galaxy populations representing different evolutionary stages: red sequence (RS) galaxies, blue cloud (BC) galaxies, green valley (GV) galaxies, and luminous compact blue galaxies (LCBGs). For each galaxy class, we derive the projected spatial and velocity distribution and characterize the degree of subclustering. We find that RS, BC, and GV galaxies in these clusters have similar velocity distributions, but that BC and GV galaxies tend to avoid the core of the two z ≈ 0.55 clusters. GV galaxies exhibit subclustering properties similar to RS galaxies, but their radial velocity distribution is significantly platykurtic compared to the RS galaxies. The absence of GV galaxies in the cluster cores may explain their somewhat prolonged star-formation history. The LCBGs appear to have recently fallen into the cluster based on their larger velocity dispersion, absence from the cores of the clusters, and different radial velocity distribution than the RS galaxies. Both LCBG and BC galaxies show a high degree of subclustering on the smallest scales, leading us to conclude that star formation is likely triggered by galaxy-galaxy interactions during infall into the cluster.

  16. Cluster fusion-fission dynamics in the Singapore stock exchange

    Science.gov (United States)

    Teh, Boon Kin; Cheong, Siew Ann

    2015-10-01

    In this paper, we investigate how the cross-correlations between stocks in the Singapore stock exchange (SGX) evolve over 2008 and 2009 within overlapping one-month time windows. In particular, we examine how these cross-correlations change before, during, and after the Sep-Oct 2008 Lehman Brothers Crisis. To do this, we extend the complete-linkage hierarchical clustering algorithm, to obtain robust clusters of stocks with stronger intracluster correlations, and weaker intercluster correlations. After we identify the robust clusters in all time windows, we visualize how these change in the form of a fusion-fission diagram. Such a diagram depicts graphically how the cluster sizes evolve, the exchange of stocks between clusters, as well as how strongly the clusters mix. From the fusion-fission diagram, we see a giant cluster growing and disintegrating in the SGX, up till the Lehman Brothers Crisis in September 2008 and the market crashes of October 2008. After the Lehman Brothers Crisis, clusters in the SGX remain small for few months before giant clusters emerge once again. In the aftermath of the crisis, we also find strong mixing of component stocks between clusters. As a result, the correlation between initially strongly-correlated pairs of stocks decay exponentially with average life time of about a month. These observations impact strongly how portfolios and trading strategies should be formulated.

  17. Molecular dynamics simulations of 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide clusters and nanodrops.

    Science.gov (United States)

    Prince, Benjamin D; Tiruppathi, Pavithra; Bemish, Raymond J; Chiu, Yu-Hui; Maginn, Edward J

    2015-01-15

    Atomistic molecular dynamics simulations of small clusters and nanodroplets of the ionic liquid 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide [EMIM-Tf2N] subject to an external electric field were performed. A 125-ion-pair droplet was found to be nearly spherical with an isotropic distribution of cations and anions under vacuum conditions. The droplet was subjected to external electric fields of varying strength, and ion emission events were observed. The initially spherical droplet is elongated along the electric field axis, resulting in nonspherical behavior and increased net dipole values after the application of strong electric fields. The critical electric field required for ion field emission was determined to be 0.985 V/nm, in agreement with the experimental value of 1.0 V/nm. Excellent agreement is found in the prediction of ionic emission products for a neutral 125-ion-pair droplet of the ionic liquid at an electric field strength of 1.2 V/nm when compared to the results of two independent experiments. Small ionic liquid clusters were investigated with respect to their thermal stabilities and were found to be thermally stable well above room temperature. The role of electric fields in the dissociation of small charged ion clusters was also investigated.

  18. Photodissociation dynamics of the Kr-HBr cluster: the effect of the rare gas atom substitution.

    Science.gov (United States)

    López-López, S; García-Vela, A

    2004-01-08

    The ultraviolet photolysis dynamics of Kr-HBr(v=0) is investigated by means of wave packet calculations, focusing on the fragmentation pathway Kr-HBr+ variant Planck's over 2pi omega-->H+Kr-Br. Photolysis is simulated by starting from two different cluster initial states, namely the ground van der Waals (vdW) and an excited vdW bending state, associated with the Kr-H-Br and Kr-Br-H isomers, respectively. The results show that, for the two initial states of the cluster, the Kr-Br product yield is lower than that of Ar-Br radicals found in previous studies on Ar-HBr photolysis. Despite this decrease, the Kr-Br yield is found to be still rather high, in particular for the initial excited vdW state of Kr-HBr(v=0). In addition, the Kr-Br product state distributions exhibit a remarkably higher excitation (mainly rotational) than the corresponding Ar-Br distributions. The lower yield and higher excitation of Kr-Br as compared to Ar-Br, are attributed to a larger share of the energy available for the radical going to internal excitation in the case of the Kr-Br product. The different partition of the energy available for Kr-Br also causes significant deviations in the photolysis behavior of Kr-HBr when compared to that of Ar-HBr, in the case of the initial excited vdW state of both clusters. A common feature of the photodissociation of Kr-HBr and Ar-HBr is the manifestation of quantum interference effects in the Kr-Br and Ar-Br rotational state distributions, in the form of pronounced structures of supernumerary rotational rainbows. (c) 2004 American Institute of Physics

  19. Planck intermediate results: XLIII. Spectral energy distribution of dust in clusters of galaxies

    DEFF Research Database (Denmark)

    Adam, R.; Ade, P. A R; Aghanim, N.

    2016-01-01

    hundred objects from the Planck cluster sample. This procedure averages out fluctuations from the IR sky, allowing us to reach a significant detection of the faint cluster contribution. We also use the large frequency range probed by Planck, together with componentseparation techniques, to remove...... content of the cluster galaxies), but the radial distribution of the emission appears to follow that of the stacked SZ signal, and thus the extent of the clusters. The recovered SED allows us to constrain the dust mass responsible for the signal and its temperature....

  20. Effects of the mean-field dynamics and the phase-space geometry on the cluster formation

    International Nuclear Information System (INIS)

    Basrak, Z.; Eudes, P.; Abgrall, P.; Haddad, F.; Sebille, F.

    1997-01-01

    A model allowing to simulate the production of clusters is developed and applied to heavy-ion reactions at intermediate energies. The model investigates the geometrical properties of the dynamically generated one-body phase space. The collision process is entirely governed by the Landau-Vlasov model, which provides the time evolution of the one-body phase-space distribution. Particles emitted during successive time intervals of the dynamics are gathered together into subensembles to which a clusterization procedure is applied. Comparison with the experimental data for the Ar(65 MeV/nucleon) + Al reaction shows that the average behaviour of particle-dependent global observables is correctly reproduced within this framework. These results point out that the studied global properties of heavy-ion collisions greatly rely on the dynamical effects of the primary non-steady stage of the nuclear reaction. (orig.)

  1. The dynamics of cavity clusters in ultrasonic (vibratory) cavitation erosion

    DEFF Research Database (Denmark)

    Hansson, I.; Mørch, Knud Aage

    1980-01-01

    The erosion of solids caused by cavitating liquids is a result of the concerted collapse of clusters of cavities. In vibratory cavitation equipment the clusters grow and collapse adjacent to a solid surface and are typically of hemispherical or cylindrical form. In the present paper the collapse...... process of these clusters is described and the collapse equations are developed and solved. The theoretical results are compared with results from high-speed photography of the clusters and with the initial stages of cavitation erosion on metal specimens. Experimental and theoretical results show...... the ambient pressure. Therefore the collapse velocity of the individual cavities increases towards the cluster center, which explains that the erosion, being caused by the individual cavities, occurs predominantly in this region. Likewise, the pressure increase at the cluster boundary explains why materials...

  2. The Atacama Cosmology Telescope: Dynamical Masses for 44 SZ-Selected Galaxy Clusters over 755 Square Degrees

    Science.gov (United States)

    Sifon, Cristobal; Battaglia, Nick; Hasselfield, Matthew; Menanteau, Felipe; Barrientos, L. Felipe; Bond, J. Richard; Crichton, Devin; Devlin, Mark J.; Dunner, Rolando; Hilton, Matt; hide

    2016-01-01

    We present galaxy velocity dispersions and dynamical mass estimates for 44 galaxy clusters selected via the Sunyaev-Zeldovich (SZ) effect by the Atacama Cosmology Telescope. Dynamical masses for 18 clusters are reported here for the first time. Using N-body simulations, we model the different observing strategies used to measure the velocity dispersions and account for systematic effects resulting from these strategies. We find that the galaxy velocity distributions may be treated as isotropic, and that an aperture correction of up to 7 per cent in the velocity dispersion is required if the spectroscopic galaxy sample is sufficiently concentrated towards the cluster centre. Accounting for the radial profile of the velocity dispersion in simulations enables consistent dynamical mass estimates regardless of the observing strategy. Cluster masses M200 are in the range (1 - 15) times 10 (sup 14) Solar Masses. Comparing with masses estimated from the SZ distortion assuming a gas pressure profile derived from X-ray observations gives a mean SZ-to-dynamical mass ratio of 1:10 plus or minus 0:13, but there is an additional 0.14 systematic uncertainty due to the unknown velocity bias; the statistical uncertainty is dominated by the scatter in the mass-velocity dispersion scaling relation. This ratio is consistent with previous determinations at these mass scales.

  3. A Dynamic Fuzzy Cluster Algorithm for Time Series

    Directory of Open Access Journals (Sweden)

    Min Ji

    2013-01-01

    clustering time series by introducing the definition of key point and improving FCM algorithm. The proposed algorithm works by determining those time series whose class labels are vague and further partitions them into different clusters over time. The main advantage of this approach compared with other existing algorithms is that the property of some time series belonging to different clusters over time can be partially revealed. Results from simulation-based experiments on geographical data demonstrate the excellent performance and the desired results have been obtained. The proposed algorithm can be applied to solve other clustering problems in data mining.

  4. Multiple co-clustering based on nonparametric mixture models with heterogeneous marginal distributions.

    Science.gov (United States)

    Tokuda, Tomoki; Yoshimoto, Junichiro; Shimizu, Yu; Okada, Go; Takamura, Masahiro; Okamoto, Yasumasa; Yamawaki, Shigeto; Doya, Kenji

    2017-01-01

    We propose a novel method for multiple clustering, which is useful for analysis of high-dimensional data containing heterogeneous types of features. Our method is based on nonparametric Bayesian mixture models in which features are automatically partitioned (into views) for each clustering solution. This feature partition works as feature selection for a particular clustering solution, which screens out irrelevant features. To make our method applicable to high-dimensional data, a co-clustering structure is newly introduced for each view. Further, the outstanding novelty of our method is that we simultaneously model different distribution families, such as Gaussian, Poisson, and multinomial distributions in each cluster block, which widens areas of application to real data. We apply the proposed method to synthetic and real data, and show that our method outperforms other multiple clustering methods both in recovering true cluster structures and in computation time. Finally, we apply our method to a depression dataset with no true cluster structure available, from which useful inferences are drawn about possible clustering structures of the data.

  5. Multiple co-clustering based on nonparametric mixture models with heterogeneous marginal distributions.

    Directory of Open Access Journals (Sweden)

    Tomoki Tokuda

    Full Text Available We propose a novel method for multiple clustering, which is useful for analysis of high-dimensional data containing heterogeneous types of features. Our method is based on nonparametric Bayesian mixture models in which features are automatically partitioned (into views for each clustering solution. This feature partition works as feature selection for a particular clustering solution, which screens out irrelevant features. To make our method applicable to high-dimensional data, a co-clustering structure is newly introduced for each view. Further, the outstanding novelty of our method is that we simultaneously model different distribution families, such as Gaussian, Poisson, and multinomial distributions in each cluster block, which widens areas of application to real data. We apply the proposed method to synthetic and real data, and show that our method outperforms other multiple clustering methods both in recovering true cluster structures and in computation time. Finally, we apply our method to a depression dataset with no true cluster structure available, from which useful inferences are drawn about possible clustering structures of the data.

  6. Multiple co-clustering based on nonparametric mixture models with heterogeneous marginal distributions

    Science.gov (United States)

    Yoshimoto, Junichiro; Shimizu, Yu; Okada, Go; Takamura, Masahiro; Okamoto, Yasumasa; Yamawaki, Shigeto; Doya, Kenji

    2017-01-01

    We propose a novel method for multiple clustering, which is useful for analysis of high-dimensional data containing heterogeneous types of features. Our method is based on nonparametric Bayesian mixture models in which features are automatically partitioned (into views) for each clustering solution. This feature partition works as feature selection for a particular clustering solution, which screens out irrelevant features. To make our method applicable to high-dimensional data, a co-clustering structure is newly introduced for each view. Further, the outstanding novelty of our method is that we simultaneously model different distribution families, such as Gaussian, Poisson, and multinomial distributions in each cluster block, which widens areas of application to real data. We apply the proposed method to synthetic and real data, and show that our method outperforms other multiple clustering methods both in recovering true cluster structures and in computation time. Finally, we apply our method to a depression dataset with no true cluster structure available, from which useful inferences are drawn about possible clustering structures of the data. PMID:29049392

  7. The shape of velocity dispersion profiles and the dynamical state of galaxy clusters

    Science.gov (United States)

    Costa, A. P.; Ribeiro, A. L. B.; de Carvalho, R. R.

    2018-01-01

    Motivated by the existence of the relationship between the dynamical state of clusters and the shape of the velocity dispersion profiles (VDPs), we study the VDPs for Gaussian (G) and non-Gaussian (NG) systems for a subsample of clusters from the Yang catalogue. The groups cover a redshift interval of 0.03 ≤ z ≤ 0.1 with halo mass ≥1014 M⊙. We use a robust statistical method, Hellinger Distance, to classify the dynamical state of the systems according to their velocity distribution. The stacked VDP of each class, G and NG, is then determined using either Bright or Faint galaxies. The stacked VDP for G groups displays a central peak followed by a monotonically decreasing trend which indicates a predominance of radial orbits, with the Bright stacked VDP showing lower velocity dispersions in all radii. The distinct features we find in NG systems are manifested not only by the characteristic shape of VDP, with a depression in the central region, but also by a possible higher infall rate associated with galaxies in the Faint stacked VDP.

  8. Angular distributions of particles sputtered from multicomponent targets with gas cluster ions

    Energy Technology Data Exchange (ETDEWEB)

    Ieshkin, A.E. [Faculty of Physics, Lomonosov Moscow State University, Leninskie Gory, Moscow 119991 (Russian Federation); Ermakov, Yu.A., E-mail: yuriermak@yandex.ru [Skobeltsyn Nuclear Physics Research Institute, Lomonosov Moscow State University, Leninskie Gory, Moscow 119991 (Russian Federation); Chernysh, V.S. [Faculty of Physics, Lomonosov Moscow State University, Leninskie Gory, Moscow 119991 (Russian Federation)

    2015-07-01

    The experimental angular distributions of atoms sputtered from polycrystalline W, Cd and Ni based alloys with 10 keV Ar cluster ions are presented. RBS was used to analyze a material deposited on a collector. It has been found that the mechanism of sputtering, connected with elastic properties of materials, has a significant influence on the angular distributions of sputtered components. The effect of non-stoichiometric sputtering at different emission angles has been found for the alloys under cluster ion bombardment. Substantial smoothing of the surface relief was observed for all targets irradiated with cluster ions.

  9. State selective dynamics of molecules, clusters, and nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Keto, John W. [Univ. of Texas, Austin, TX (United States)

    2005-06-01

    Early objectives of this grant were: (1) Measure two-photon excitation of even parity excitons in liquid an solid xenon, (2) Study state-to-state energy transver between two-photon laser excited states or rare-gas atoms to other rare has atoms, (3) study reactive half-collisions between xenon and chlorine leading to the XeCl* B state, (4) measure the spectra of ro-vibrational states of cluster ions and radicals formed in high-pressure discharges and to study their dynamics, (5) measure the surface and bulk electronic states of nanoparticles produced by a unique method of synthesis--laser ablation of microspheres (LAM). Using near-field and microluminescence techniques, we obtained spectra of single nanocrystals to compare with spectra obtained in a supersonic jet apparatus using resonance excitation followed by photoionization (REMPI) with time-of-flight mass analysis. These materials combine the functional advantages obtained from the size-tunable properties of nanocomposite materials with the fabrication and direct-write advantages of NPs manufactured by LAM. We demostrated that CdSe nanoparticles produced by LAM were efficiient fluorescers, even when deposited dry on sapphire substrates. Si nanoparticles were fluorescent when captured in ethylene glycol. We also obtiained efficient fluorescence from Er doped phosphate glass nanopartiicles which have application to gain wafeguides in integrated optics or to nanoslush lasers. We used a femptosecond laser to study the nonlinear spectra of NC composites. We are currently measuring fluorescence and second and third-order susceptibilities of composites of Ag, Si, and GaN nanoparticles encapsulated within thin films of sapphire or SiO 2.

  10. State selective dynamics of molecules, clusters, and nanostructures

    International Nuclear Information System (INIS)

    John W. Keto

    2005-01-01

    Early objectives of this grant were: (1) Measure two-photon excitation of even parity excitons in liquid an solid xenon, (2) Study state-to-state energy transfer between two-photon laser excited states or rare-gas atoms to other rare has atoms, (3) study reactive half-collisions between xenon and chlorine leading to the XeCl* B state, (4) measure the spectra of ro-vibrational states of cluster ions and radicals formed in high-pressure discharges and to study their dynamics, (5) measure the surface and bulk electronic states of nanoparticles produced by a unique method of synthesis--laser ablation of microspheres (LAM). Using near-field and microluminescence techniques, we obtained spectra of single nanocrystals to compare with spectra obtained in a supersonic jet apparatus using resonance excitation followed by photoionization (REMPI) with time-of-flight mass analysis. These materials combine the functional advantages obtained from the size-tunable properties of nanocomposite materials with the fabrication and direct-write advantages of NPs manufactured by LAM. We demonstrated that CdSe nanoparticles produced by LAM were efficient fluorescers, even when deposited dry on sapphire substrates. Si nanoparticles were fluorescent when captured in ethylene glycol. We also obtained efficient fluorescence from Er doped phosphate glass nanoparticles which have application to gain waveguides in integrated optics or to nanoslush lasers. We used a femptosecond laser to study the nonlinear spectra of NC composites. We are currently measuring fluorescence and second and third-order susceptibilities of composites of Ag, Si, and GaN nanoparticles encapsulated within thin films of sapphire or SiO2

  11. Approximate Solutions of Interactive Dynamic Influence Diagrams Using Model Clustering

    DEFF Research Database (Denmark)

    Zeng, Yifeng; Doshi, Prashant; Qiongyu, Cheng

    2007-01-01

    of the other agents, which increase exponentially with the number of time steps. We present a method of solving I-DIDs approximately by limiting the number of other agents' candidate models at each time step to a constant. We do this by clustering the models and selecting a representative set from the clusters...

  12. Atomistic interactions of clusters on surfaces using molecular dynamics and hyper molecular dynamics

    International Nuclear Information System (INIS)

    Sanz-Navarro, Carlos F.

    2002-01-01

    The work presented in this thesis describes the results of Molecular Dynamics (MD) simulations applied to the interaction of silver clusters with graphite surfaces and some numerical and theoretical methods concerning the extension of MD simulations to longer time scales (hyper-MD). The first part of this thesis studies the implantation of clusters at normal incidence onto a graphite surface in order to determine the scaling of the penetration depth (PD) against the impact energy. A comparison with experimental results is made with good agreement. The main physical observations of the impact process are described and analysed. It is shown that there is a threshold impact velocity above which the linear dependence on PD on impact energy changes to a linear dependence on velocity. Implantation of silver clusters at oblique incidence is also considered. The second part of this work analyses the validity and feasibility of the three minimisation methods for the hyper-MD simulation method whereby time scales of an MD simulation can be extended. A correct mathematical basis for the iterative method is derived. It is found that one of the iterative methods, upon which hyper-lD is based, is very likely to fail in high-dimensional situations because it requires a too expensive convergence. Two new approximations to the hyper-MD approach are proposed, which reduce the computational effort considerably. Both approaches, although not exact, can help to search for some of the most likely transitions in the system. Some examples are given to illustrate this. (author)

  13. Performance prediction model for distributed applications on multicore clusters

    CSIR Research Space (South Africa)

    Khanyile, NP

    2012-07-01

    Full Text Available Distributed processing offers a way of successfully dealing with computationally demanding applications such as scientific problems. Over the years, researchers have investigated ways to predict the performance of parallel algorithms. Amdahl’s law...

  14. Dynamical Models For Prices With Distributed Delays

    Directory of Open Access Journals (Sweden)

    Mircea Gabriela

    2015-06-01

    Full Text Available In the present paper we study some models for the price dynamics of a single commodity market. The quantities of supplied and demanded are regarded as a function of time. Nonlinearities in both supply and demand functions are considered. The inventory and the level of inventory are taken into consideration. Due to the fact that the consumer behavior affects commodity demand, and the behavior is influenced not only by the instantaneous price, but also by the weighted past prices, the distributed time delay is introduced. The following kernels are taken into consideration: demand price weak kernel and demand price Dirac kernel. Only one positive equilibrium point is found and its stability analysis is presented. When the demand price kernel is weak, under some conditions of the parameters, the equilibrium point is locally asymptotically stable. When the demand price kernel is Dirac, the existence of the local oscillations is investigated. A change in local stability of the equilibrium point, from stable to unstable, implies a Hopf bifurcation. A family of periodic orbits bifurcates from the positive equilibrium point when the time delay passes through a critical value. The last part contains some numerical simulations to illustrate the effectiveness of our results and conclusions.

  15. Mass distribution and multiple fragmentation events in high energy cluster-cluster collisions: evidence for a predicted phase transition

    International Nuclear Information System (INIS)

    Farizon, B.; Farizon, M.; Gaillard, M.J.; Genre, R.; Louc, S.; Martin, J.; Senn, G.; Scheier, P.; Maerk, T.D.

    1996-09-01

    Fragment size distributions including multiple fragmentation events have been measured for high energy H 25 + cluster ions (60 keV/amu) colliding with a neutral C 60 target. In contrast to earlier collision experiments with a helium target the present studies do not show a U-shaped fragment mass distribution, but a single power-law falloff with increasing fragment mass. This behaviour is similar to what is known for the intermediate regime in nuclear collision physics and thus confirms a recently predicted scaling from nuclear to molecular collisions

  16. The Distribution and Ages of Star Clusters in the Small Magellanic Cloud: Constraints on the Interaction History of the Magellanic Clouds

    Science.gov (United States)

    Bitsakis, Theodoros; González-Lópezlira, R. A.; Bonfini, P.; Bruzual, G.; Maravelias, G.; Zaritsky, D.; Charlot, S.; Ramírez-Siordia, V. H.

    2018-02-01

    We present a new study of the spatial distribution and ages of the star clusters in the Small Magellanic Cloud (SMC). To detect and estimate the ages of the star clusters we rely on the new fully automated method developed by Bitsakis et al. Our code detects 1319 star clusters in the central 18 deg2 of the SMC we surveyed (1108 of which have never been reported before). The age distribution of those clusters suggests enhanced cluster formation around 240 Myr ago. It also implies significant differences in the cluster distribution of the bar with respect to the rest of the galaxy, with the younger clusters being predominantly located in the bar. Having used the same setup, and data from the same surveys as for our previous study of the LMC, we are able to robustly compare the cluster properties between the two galaxies. Our results suggest that the bulk of the clusters in both galaxies were formed approximately 300 Myr ago, probably during a direct collision between the two galaxies. On the other hand, the locations of the young (≤50 Myr) clusters in both Magellanic Clouds, found where their bars join the H I arms, suggest that cluster formation in those regions is a result of internal dynamical processes. Finally, we discuss the potential causes of the apparent outside-in quenching of cluster formation that we observe in the SMC. Our findings are consistent with an evolutionary scheme where the interactions between the Magellanic Clouds constitute the major mechanism driving their overall evolution.

  17. Dynamical transitions in large systems of mean field-coupled Landau-Stuart oscillators: Extensive chaos and cluster states

    Energy Technology Data Exchange (ETDEWEB)

    Ku, Wai Lim; Girvan, Michelle; Ott, Edward [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742 (United States)

    2015-12-15

    In this paper, we study dynamical systems in which a large number N of identical Landau-Stuart oscillators are globally coupled via a mean-field. Previously, it has been observed that this type of system can exhibit a variety of different dynamical behaviors. These behaviors include time periodic cluster states in which each oscillator is in one of a small number of groups for which all oscillators in each group have the same state which is different from group to group, as well as a behavior in which all oscillators have different states and the macroscopic dynamics of the mean field is chaotic. We argue that this second type of behavior is “extensive” in the sense that the chaotic attractor in the full phase space of the system has a fractal dimension that scales linearly with N and that the number of positive Lyapunov exponents of the attractor also scales linearly with N. An important focus of this paper is the transition between cluster states and extensive chaos as the system is subjected to slow adiabatic parameter change. We observe discontinuous transitions between the cluster states (which correspond to low dimensional dynamics) and the extensively chaotic states. Furthermore, examining the cluster state, as the system approaches the discontinuous transition to extensive chaos, we find that the oscillator population distribution between the clusters continually evolves so that the cluster state is always marginally stable. This behavior is used to reveal the mechanism of the discontinuous transition. We also apply the Kaplan-Yorke formula to study the fractal structure of the extensively chaotic attractors.

  18. Ab Initio Molecular Dynamics Studies of Pb m Sb n ( m + n ≤ 9) Alloy Clusters

    Science.gov (United States)

    Song, Bingyi; Xu, Baoqiang; Yang, Bin; Jiang, Wenlong; Chen, Xiumin; Xu, Na; Liu, Dachun; Dai, Yongnian

    2017-10-01

    Structure, stability, and dynamics of Pb m Sb n ( m + n ≤ 9) clusters were investigated using ab initio molecular dynamics. Size dependence of binding energies, the second-order energy difference of clusters, dissociation energy, HOMO-LUMO gaps, Mayer bond order, and the diffusion coefficient of Pb m Sb n clusters were discussed. Results suggest that Pb3Sb2, Pb4Sb2, and Pb5Sb4 ( n = 2 or 4) clusters have higher stability than other clusters, which is consistent with previous findings. In case of Pb-Sb alloy, the dynamics results show that Pb4Sb2 (Pb-22.71 wt pct Sb) can exist in gas phase at 1073 K (800 °C), which reasonably explains the azeotropic phenomenon, and the calculated values are in agreement with the experimental results (Pb-22 wt pct Sb).

  19. Transition from monomeric phase to dynamic cluster phase in lysozyme protein solutions

    Science.gov (United States)

    Liu, Yun; Falus, Peter; Porcar, Lionel; Fratini, Emiliano; Chen, Wei-Ren; Faraone, Antonio; Hong, Kunlun; Baglioni, Piero

    2013-03-01

    Intermediate range order (IRO) has been recently observed in lysozyme solution that is caused by a combination of a short-range attraction and long-range repulsion. At very high concentration, there is observed cluster formation in lysozyme solutions that is one type of IRO structures. Here, we investigate the temperature effect on the dynamic cluster formation and identify the transition concentration from a monomeric protein phase to a cluster phase. The normalized short-time self-diffusion coefficient is not affected by changing attraction strength at the concentration of about 10% mass fraction, indicating that the system is still dominated by monomeric protein phase. However, at high concentrations, the average self-diffusion coefficient is sensitive to the change of short-range attraction strength, which is interpreted due to the growth of the size of dynamic clusters in solution. The transition concentration from dominating monomeric phase to dynamic cluster phase is estimated to be around 14 % mass fraction.

  20. One- and two-cluster synchronized dynamics of non-diffusively coupled Tchebycheff map networks

    International Nuclear Information System (INIS)

    Schäfer, Mirko; Greiner, Martin

    2012-01-01

    We use the master stability formalism to discuss one- and two-cluster synchronization of coupled Tchebycheff map networks. For diffusively coupled map systems, the one-cluster synchronized dynamics is given by the behaviour of the individual maps, and the coupling only determines the stability of the coherent state. For the case of non-diffusive coupling and for two-cluster synchronization, the synchronized dynamics on networks is different from the behaviour of the single individual map. Depending on the coupling, we study numerically the characteristics of various forms of the resulting synchronized dynamics. The stability properties of the respective one-cluster synchronized states are discussed for arbitrary network structures. For the case of two-cluster synchronization on bipartite networks we also present analytical expressions for fixed points and zig-zag patterns, and explicitly determine the linear stability of these orbits for the special case of ring-networks.

  1. A robust approach based on Weibull distribution for clustering gene expression data

    Directory of Open Access Journals (Sweden)

    Gong Binsheng

    2011-05-01

    Full Text Available Abstract Background Clustering is a widely used technique for analysis of gene expression data. Most clustering methods group genes based on the distances, while few methods group genes according to the similarities of the distributions of the gene expression levels. Furthermore, as the biological annotation resources accumulated, an increasing number of genes have been annotated into functional categories. As a result, evaluating the performance of clustering methods in terms of the functional consistency of the resulting clusters is of great interest. Results In this paper, we proposed the WDCM (Weibull Distribution-based Clustering Method, a robust approach for clustering gene expression data, in which the gene expressions of individual genes are considered as the random variables following unique Weibull distributions. Our WDCM is based on the concept that the genes with similar expression profiles have similar distribution parameters, and thus the genes are clustered via the Weibull distribution parameters. We used the WDCM to cluster three cancer gene expression data sets from the lung cancer, B-cell follicular lymphoma and bladder carcinoma and obtained well-clustered results. We compared the performance of WDCM with k-means and Self Organizing Map (SOM using functional annotation information given by the Gene Ontology (GO. The results showed that the functional annotation ratios of WDCM are higher than those of the other methods. We also utilized the external measure Adjusted Rand Index to validate the performance of the WDCM. The comparative results demonstrate that the WDCM provides the better clustering performance compared to k-means and SOM algorithms. The merit of the proposed WDCM is that it can be applied to cluster incomplete gene expression data without imputing the missing values. Moreover, the robustness of WDCM is also evaluated on the incomplete data sets. Conclusions The results demonstrate that our WDCM produces clusters

  2. Cam Gears Dynamics in the Classic Distribution

    Directory of Open Access Journals (Sweden)

    Florian Ion Petrescu

    2014-01-01

    Full Text Available Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 The paper presents an original method to determine the general dynamics of mechanisms with rotation cams and followers, particularized to the plate translated follower. First, one presents the dynamics kinematics. Then one solves the Lagrange equation and with an original dynamic model with one degree of freedom, with variable internal amortization, it makes the dynamic analysis of two models.

  3. Baryon Distribution in Galaxy Clusters as a Result of Sedimentation of Helium Nuclei.

    Science.gov (United States)

    Qin; Wu

    2000-01-20

    Heavy particles in galaxy clusters tend to be more centrally concentrated than light ones according to the Boltzmann distribution. An estimate of the drift velocity suggests that it is possible that the helium nuclei may have entirely or partially sedimented into the cluster core within the Hubble time. We demonstrate this scenario using the Navarro-Frenk-White profile as the dark matter distribution of clusters and assuming that the intracluster gas is isothermal and in hydrostatic equilibrium. We find that a greater fraction of baryonic matter is distributed at small radii than at large radii, which challenges the prevailing claim that the baryon fraction increases monotonically with cluster radius. It shows that the conventional mass estimate using X-ray measurements of intracluster gas along with a constant mean molecular weight may have underestimated the total cluster mass by approximately 20%, which in turn leads to an overestimate of the total baryon fraction by the same percentage. Additionally, it is pointed out that the sedimentation of helium nuclei toward cluster cores may at least partially account for the sharp peaks in the central X-ray emissions observed in some clusters.

  4. Real-Time Reactive Power Distribution in Microgrids by Dynamic Programing

    DEFF Research Database (Denmark)

    Levron, Yoash; Beck, Yuval; Katzir, Liran

    2017-01-01

    In this paper a new real-time optimization method for reactive power distribution in microgrids is proposed. The method enables location of a globally optimal distribution of reactive power under normal operating conditions. The method exploits the typical compact structure of microgrids to obtain...... as radial ones. The optimization problem is formulated with the cluster reactive powers as free variables, and the solution space is spanned by the cluster reactive power outputs. The optimal solution is then constructed by efficiently scanning the entire solution space, by scanning every possible...... combination of reactive powers, by means of dynamic programming. Since every single step involves a one-dimensional problem, the complexity of the solution is only linear with the number of clusters, and as a result, a globally optimal solution may be obtained in real time. The paper includes the results...

  5. The distribution of early- and late-type galaxies in the Coma cluster

    Science.gov (United States)

    Doi, M.; Fukugita, M.; Okamura, S.; Turner, E. L.

    1995-01-01

    The spatial distribution and the morohology-density relation of Coma cluster galaxies are studied using a new homogeneous photmetric sample of 450 galaxies down to B = 16.0 mag with quantitative morphology classification. The sample covers a wide area (10 deg X 10 deg), extending well beyond the Coma cluster. Morphological classifications into early- (E+SO) and late-(S) type galaxies are made by an automated algorithm using simple photometric parameters, with which the misclassification rate is expected to be approximately 10% with respect to early and late types given in the Third Reference Catalogue of Bright Galaxies. The flattened distribution of Coma cluster galaxies, as noted in previous studies, is most conspicuously seen if the early-type galaxies are selected. Early-type galaxies are distributed in a thick filament extended from the NE to the WSW direction that delineates a part of large-scale structure. Spiral galaxies show a distribution with a modest density gradient toward the cluster center; at least bright spiral galaxies are present close to the center of the Coma cluster. We also examine the morphology-density relation for the Coma cluster including its surrounding regions.

  6. Ckmeans.1d.dp: Optimal k-means Clustering in One Dimension by Dynamic Programming.

    Science.gov (United States)

    Wang, Haizhou; Song, Mingzhou

    2011-12-01

    The heuristic k -means algorithm, widely used for cluster analysis, does not guarantee optimality. We developed a dynamic programming algorithm for optimal one-dimensional clustering. The algorithm is implemented as an R package called Ckmeans.1d.dp . We demonstrate its advantage in optimality and runtime over the standard iterative k -means algorithm.

  7. An adaptive immune optimization algorithm with dynamic lattice searching operation for fast optimization of atomic clusters

    International Nuclear Information System (INIS)

    Wu, Xia; Wu, Genhua

    2014-01-01

    Highlights: • A high efficient method for optimization of atomic clusters is developed. • Its performance is studied by optimizing Lennard-Jones clusters and Ag clusters. • The method is proved to be quite efficient. • A new Ag 61 cluster with stacking-fault face-centered cubic motif is found. - Abstract: Geometrical optimization of atomic clusters is performed by a development of adaptive immune optimization algorithm (AIOA) with dynamic lattice searching (DLS) operation (AIOA-DLS method). By a cycle of construction and searching of the dynamic lattice (DL), DLS algorithm rapidly makes the clusters more regular and greatly reduces the potential energy. DLS can thus be used as an operation acting on the new individuals after mutation operation in AIOA to improve the performance of the AIOA. The AIOA-DLS method combines the merit of evolutionary algorithm and idea of dynamic lattice. The performance of the proposed method is investigated in the optimization of Lennard-Jones clusters within 250 atoms and silver clusters described by many-body Gupta potential within 150 atoms. Results reported in the literature are reproduced, and the motif of Ag 61 cluster is found to be stacking-fault face-centered cubic, whose energy is lower than that of previously obtained icosahedron

  8. An adaptive immune optimization algorithm with dynamic lattice searching operation for fast optimization of atomic clusters

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Xia, E-mail: xiawu@mail.nankai.edu.cn; Wu, Genhua

    2014-08-31

    Highlights: • A high efficient method for optimization of atomic clusters is developed. • Its performance is studied by optimizing Lennard-Jones clusters and Ag clusters. • The method is proved to be quite efficient. • A new Ag{sub 61} cluster with stacking-fault face-centered cubic motif is found. - Abstract: Geometrical optimization of atomic clusters is performed by a development of adaptive immune optimization algorithm (AIOA) with dynamic lattice searching (DLS) operation (AIOA-DLS method). By a cycle of construction and searching of the dynamic lattice (DL), DLS algorithm rapidly makes the clusters more regular and greatly reduces the potential energy. DLS can thus be used as an operation acting on the new individuals after mutation operation in AIOA to improve the performance of the AIOA. The AIOA-DLS method combines the merit of evolutionary algorithm and idea of dynamic lattice. The performance of the proposed method is investigated in the optimization of Lennard-Jones clusters within 250 atoms and silver clusters described by many-body Gupta potential within 150 atoms. Results reported in the literature are reproduced, and the motif of Ag{sub 61} cluster is found to be stacking-fault face-centered cubic, whose energy is lower than that of previously obtained icosahedron.

  9. Dynamics of a nanometer-sized uranyl cluster in solution

    International Nuclear Information System (INIS)

    Johnson, Rene L.; Ohlin, C. Andre; Pellegrini, Kristi; Burns, Peter C.; Casey, William H.

    2013-01-01

    A class of uranyl peroxide clusters was discovered before as nanometer-sized ions that form spontaneously in aqueous solutions. The uranyl(VI) cluster investigated here is approximately 2 nm in diameter, contains 24 uranyl moieties, and 12 pyrophosphate units. NMR spectroscopy shows that the ion has two distinct forms that interconvert in milliseconds to seconds depending on the temperature and the size of the counterions. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. DCE: A Distributed Energy-Efficient Clustering Protocol for Wireless Sensor Network Based on Double-Phase Cluster-Head Election.

    Science.gov (United States)

    Han, Ruisong; Yang, Wei; Wang, Yipeng; You, Kaiming

    2017-05-01

    Clustering is an effective technique used to reduce energy consumption and extend the lifetime of wireless sensor network (WSN). The characteristic of energy heterogeneity of WSNs should be considered when designing clustering protocols. We propose and evaluate a novel distributed energy-efficient clustering protocol called DCE for heterogeneous wireless sensor networks, based on a Double-phase Cluster-head Election scheme. In DCE, the procedure of cluster head election is divided into two phases. In the first phase, tentative cluster heads are elected with the probabilities which are decided by the relative levels of initial and residual energy. Then, in the second phase, the tentative cluster heads are replaced by their cluster members to form the final set of cluster heads if any member in their cluster has more residual energy. Employing two phases for cluster-head election ensures that the nodes with more energy have a higher chance to be cluster heads. Energy consumption is well-distributed in the proposed protocol, and the simulation results show that DCE achieves longer stability periods than other typical clustering protocols in heterogeneous scenarios.

  11. Generation of clusters in complex dynamical networks via pinning control

    International Nuclear Information System (INIS)

    Li Kezan; Fu Xinchu; Small, Michael

    2008-01-01

    Many real-world networks show community structure, i.e., groups (or clusters) of nodes that have a high density of links within them but with a lower density of links between them. In this paper, by applying feedback injections to a fraction of network nodes, various clusters are synchronized independently according to the community structure generated by the group partition of the network (cluster synchronization). This control is achieved by pinning (i.e. applying linear feedback control) to a subset of the network nodes. Those pinned nodes are selected not randomly but according to the topological structure of communities of a given network. Specifically, for a given group partition of a network, those nodes with direct connections between groups must be pinned in order to achieve cluster synchronization. Both the local stability and global stability of cluster synchronization are investigated. Taking the tree-shaped network and the most modular network as two particular examples, we illustrate in detail how the pinning strategy influences the generation of clusters. The simulations verify the efficiency of the pinning schemes used in this paper

  12. Dynamics and stability of charged clusters and droplets

    International Nuclear Information System (INIS)

    Manil, B.; Lebius, H.; Chandezon, F.; Huber, B.A.; Duft, D.; Leisner, T.; Guet, C.

    2002-01-01

    Lord Raleigh predicted (Phil. Mag. 14, 184(1982) ) that a charged, incompressible liquid droplet becomes unstable as soon as the cohesive forces, which create the surface tension and which try to keep the droplet in its spherical form, are equal to the Coulomb forces, which try to destabilise it. This means that that the Coulomb energy E c corresponds to twice the surface energy E s . The ratio X = E c / 2 E s (feasibility), thus characterising the Raleigh limit by X = 1. In order to test its validity, metal clusters were ionized in collisions with highly charged ions, allowing for the first time to prepare charged systems with a feasibility greater than 1. Multiply charged sodium clusters were produced through collisions of Ar 11+ or Xe 28+ with neutral sodium clusters. It was observed, with increasing cluster charge and consequently cluster size the detected system indeed approach the Raleigh limit (for q = 10 X = 0.85). However, it was not reached due to the initial cluster temperature and the energy transfer in the collision. Subsequent, the stability and the explosion of highly charge microdroplets which were injected into a Paul trap levitator were studied, specifically, glycol was irradiated with a HeNe laser. It was observed that a resonance phenomena appeared just before each explosion. As the resonance is linked to X ∼ 1, this is the first proof that the Coulomb instability of charge glycol microdroplets occurs at X ∼ 1, as predicted by Lord Raleigh. (nevyjel)

  13. Dynamics of cluster structures in a financial market network

    Science.gov (United States)

    Kocheturov, Anton; Batsyn, Mikhail; Pardalos, Panos M.

    2014-11-01

    In the course of recent fifteen years the network analysis has become a powerful tool for studying financial markets. In this work we analyze stock markets of the USA and Sweden. We study cluster structures of a market network constructed from a correlation matrix of returns of the stocks traded in each of these markets. Such cluster structures are obtained by means of the P-Median Problem (PMP) whose objective is to maximize the total correlation between a set of stocks called medians of size p and other stocks. Every cluster structure is an undirected disconnected weighted graph in which every connected component (cluster) is a star, or a tree with one central node (called a median) and several leaf nodes connected with the median by weighted edges. Our main observation is that in non-crisis periods of time cluster structures change more chaotically, while during crises they show more stable behavior and fewer changes. Thus an increasing stability of a market graph cluster structure obtained via the PMP could be used as an indicator of a coming crisis.

  14. The virial mass distribution of ultradiffuse galaxies in clusters and groups

    Science.gov (United States)

    Amorisco, N. C.

    2018-03-01

    We use the observed abundances of ultradiffuse galaxies (UDGs) in clusters and groups and Λ cold dark matter subhalo mass functions to put constraints on the distribution of present-day halo masses of satellite UDGs. If all of the most massive subhaloes in the cluster host a UDG, UDGs occupy all subhaloes with log Msub/M⊙ ≳ 11. For a model in which the efficiency of UDG formation is higher around some characteristic halo mass, higher fractions of massive UDGs require larger spreads in the UDG mass distribution. In a cluster with a virial mass of 1015 M⊙, the 90 per cent upper limit for the fraction of UDGs with log Msub/M⊙ > 12 is 7 per cent, occupying 70 per cent of all cluster subhaloes above the same mass. To reproduce the observed abundances, however, the mass distribution of satellite UDGs has to be broad, with > 30 per cent having log Msub/M⊙ continuous distribution in which a majority are hosted by low-mass haloes. The abundance of satellite UDGs may fall short of the linear relation with the cluster/group mass Mhost in low-mass hosts, log Mhost/M⊙ ˜ 12. Characterizing these deviations - or the lack thereof - will allow for stringent constraints on the UDG virial mass distribution.

  15. On the equilibrium distribution of the elements in the gas in the Coma cluster

    Science.gov (United States)

    Abramopoulos, F.; Chanan, G. A.; Ku, W. H.-M.

    1981-01-01

    The equilibrium distribution of the elements for the case of an isothermal plasma in a gravitational potential well is given governing equations and a rapidly converging iterative procedure for their solution. Results are applied to the intracluster gas in clusters of galaxies, and implications are identified for the controversy as to whether iron nuclei settle out in the cluster core, and with respect to the interpretation of distribution size and shape for continuum X-ray emission from clusters. A model for the Coma cluster is considered in which the intracluster gas is in equilibrium and partially processed. It is found that this model can account for the angular dependence of the continuum X-ray emission from Coma, as determined by Einstein Observatory observations, at least as well as the uniform composition model.

  16. Energy efficient distributed cluster head scheduling scheme for two tiered wireless sensor network

    OpenAIRE

    G. Kannan; T. Sree Renga Raja

    2015-01-01

    Wireless Sensor Network (WSN) provides a significant contribution in the emerging fields such as ambient intelligence and ubiquitous computing. In WSN, optimization and load balancing of network resources are critical concern to provide the intelligence for long duration. Since clustering the sensor nodes can significantly enhance overall system scalability and energy efficiency this paper presents a distributed cluster head scheduling (DCHS) algorithm to achieve the network longevity in WSN....

  17. Schedulability Analysis and Optimization for the Synthesis of Multi-Cluster Distributed Embedded Systems

    DEFF Research Database (Denmark)

    Pop, Paul; Eles, Petru; Peng, Zebo

    2003-01-01

    We present an approach to schedulability analysis for the synthesis of multi-cluster distributed embedded systems consisting of time-triggered and event-triggered clusters, interconnected via gateways. We have also proposed a buffer size and worst case queuing delay analysis for the gateways......, responsible for routing inter-cluster traffic. Optimization heuristics for the priority assignment and synthesis of bus access parameters aimed at producing a schedulable system with minimal buffer needs have been proposed. Extensive experiments and a real-life example show the efficiency of our approaches....

  18. Schedulability Analysis and Optimization for the Synthesis of Multi-Cluster Distributed Embedded Systems

    DEFF Research Database (Denmark)

    Pop, Paul; Eles, Petru; Peng, Zebo

    2003-01-01

    An approach to schedulability analysis for the synthesis of multi-cluster distributed embedded systems consisting of time-triggered and event-triggered clusters, interconnected via gateways, is presented. A buffer size and worst case queuing delay analysis for the gateways, responsible for routing...... inter-cluster traffic, is also proposed. Optimisation heuristics for the priority assignment and synthesis of bus access parameters aimed at producing a schedulable system with minimal buffer needs have been proposed. Extensive experiments and a real-life example show the efficiency of the approaches....

  19. Cluster and single-particle distributions in nucleus-nucleus interactions

    International Nuclear Information System (INIS)

    Kulakov, B.A.; Karachuk, Yu.

    1997-01-01

    Relativistic nuclear reactions, π- - C (p beam = 40 GeV/c), Mg - Mg (p beam = 4.5 A GeV/c), and C - C (p beam = 4.2 A GeV/c), are compared by using Lorentz-invariant variables b ik . These variables are used to compare and classify nuclear reactions of various types in a wide range of energies. Different algorithms of clusters separation in the four-velocity space are compared. Experimental distributions are analyzed by means of invariant variables in the space to understand the difference of behaviour of particles and clusters for these reactions. Universal properties of hadron clusters are presented

  20. Schedulability-Driven Frame Packing for Multi-Cluster Distributed Embedded Systems

    DEFF Research Database (Denmark)

    Pop, Paul; Eles, Petru; Peng, Zebo

    2003-01-01

    We present an approach to frame packing for multi-cluster distributed embedded systems consisting of time-triggered and event-triggered clusters, interconnected via gateways. In our approach, the application messages are packed into frames such that the application is schedulable. Thus, we have...... also proposed a schedulability analysis for applications consisting of mixed event-triggered and time-triggered processes and messages, and a worst case queuing delay analysis for the gateways, responsible for routing inter-cluster traffic. Optimization heuristics for frame packing aiming at producing...

  1. Plasma flow around and charge distribution of a dust cluster in a rf discharge

    Science.gov (United States)

    Schleede, J.; Lewerentz, L.; Bronold, F. X.; Schneider, R.; Fehske, H.

    2018-04-01

    We employ a particle-in-cell Monte Carlo collision/particle-particle particle-mesh simulation to study the plasma flow around and the charge distribution of a three-dimensional dust cluster in the sheath of a low-pressure rf argon discharge. The geometry of the cluster and its position in the sheath are fixed to the experimental values, prohibiting a mechanical response of the cluster. Electrically, however, the cluster and the plasma environment, mimicking also the experimental situation, are coupled self-consistently. We find a broad distribution of the charges collected by the grains. The ion flux shows on the scale of the Debye length strong focusing and shadowing inside and outside the cluster due to the attraction of the ions to the negatively charged grains, whereas the electron flux is characterized on this scale only by a weak spatial modulation of its magnitude depending on the rf phase. On the scale of the individual dust potentials, however, the electron flux deviates in the vicinity of the cluster strongly from the laminar flow associated with the plasma sheath. It develops convection patterns to compensate for the depletion of electrons inside the dust cluster.

  2. Cluster dynamics modeling of the effect of high dose irradiation and helium on the microstructure of austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Brimbal, Daniel, E-mail: Daniel.brimbal@areva.com [AREVA NP, Tour AREVA, 1 Place Jean Millier, 92084 Paris La Défense (France); Fournier, Lionel [AREVA NP, Tour AREVA, 1 Place Jean Millier, 92084 Paris La Défense (France); Barbu, Alain [Alain Barbu Consultant, 6 Avenue Pasteur Martin Luther King, 78230 Le Pecq (France)

    2016-01-15

    A mean field cluster dynamics model has been developed in order to study the effect of high dose irradiation and helium on the microstructural evolution of metals. In this model, self-interstitial clusters, stacking-fault tetrahedra and helium-vacancy clusters are taken into account, in a configuration well adapted to austenitic stainless steels. For small helium-vacancy cluster sizes, the densities of each small cluster are calculated. However, for large sizes, only the mean number of helium atoms per cluster size is calculated. This aspect allows us to calculate the evolution of the microstructural features up to high irradiation doses in a few minutes. It is shown that the presence of stacking-fault tetrahedra notably reduces cavity sizes below 400 °C, but they have little influence on the microstructure above this temperature. The binding energies of vacancies to cavities are calculated using a new method essentially based on ab initio data. It is shown that helium has little effect on the cavity microstructure at 300 °C. However, at higher temperatures, even small helium production rates such as those typical of sodium-fast-reactors induce a notable increase in cavity density compared to an irradiation without helium. - Highlights: • Irradiation of steels with helium is studied through a new cluster dynamics model. • There is only a small effect of helium on cavity distributions in PWR conditions. • An increase in helium production causes an increase in cavity density over 500 °C. • The role of helium is to stabilize cavities via reduced emission of vacancies.

  3. Transformation dynamics of Ni clusters into NiO rings under electron beam irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Knez, Daniel, E-mail: daniel.knez@felmi-zfe.at [Institute of Electron Microscopy and Nanoanalysis, Graz University of Technology, Steyrergasse 17, 8010 Graz (Austria); Graz Centre for Electron Microscopy, Steyrergasse 17, 8010 Graz (Austria); Thaler, Philipp; Volk, Alexander [Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz (Austria); Kothleitner, Gerald [Institute of Electron Microscopy and Nanoanalysis, Graz University of Technology, Steyrergasse 17, 8010 Graz (Austria); Graz Centre for Electron Microscopy, Steyrergasse 17, 8010 Graz (Austria); Ernst, Wolfgang E. [Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz (Austria); Hofer, Ferdinand [Institute of Electron Microscopy and Nanoanalysis, Graz University of Technology, Steyrergasse 17, 8010 Graz (Austria); Graz Centre for Electron Microscopy, Steyrergasse 17, 8010 Graz (Austria)

    2017-05-15

    We report the transformation of nickel clusters into NiO rings by an electron beam induced nanoscale Kirkendall effect. High-purity nickel clusters consisting of a few thousand atoms have been used as precursors and were synthesized with the superfluid helium droplet technique. Aberration-corrected, analytical scanning transmission electron microscopy was applied to oxidise and simultaneously analyse the nanostructures. The transient dynamics of the oxidation could be documented by time lapse series using high-angle annular dark-field imaging and electron energy-loss spectroscopy. A two-step Cabrera-Mott oxidation mechanism was identified. It was found that water adsorbed adjacent to the clusters acts as oxygen source for the electron beam induced oxidation. The size-dependent oxidation rate was estimated by quantitative EELS measurements combined with molecular dynamics simulations. Our findings could serve to better control sample changes during examination in an electron microscope, and might provide a methodology to generate other metal oxide nanostructures. - Highlights: • Beam induced conversion of Ni clusters into crystalline NiO rings has been observed. • Ni clusters were grown with the superfluid He-droplet technique. • oxidizeSTEM was utilized to investigate and simultaneously oxidize these clusters. • Oxidation dynamics was captured in real-time. • Cluster sizes and the oxidation rate were estimated via EELS and molecular dynamics.

  4. A Dynamical Potential-Density Pair for Star Clusters with Nearly Isothermal Interiors

    Science.gov (United States)

    Stone, Nicholas C.; Ostriker, Jeremiah P.

    2015-06-01

    We present a potential-density pair designed to model nearly isothermal star clusters (and similar self-gravitating systems) with a central core and an outer turnover radius, beyond which density falls off as {r}-4. In the intermediate zone, the profile is similar to that of an isothermal sphere (density ρ \\propto {r}-2), somewhat less steep than the King profile, and with the advantage that many dynamical quantities can be written in a simple closed form. We derive new analytic expressions for the cluster binding energy and velocity dispersion, and apply these to create toy models for cluster core collapse and evaporation. We fit our projected surface brightness profiles to observed globular and open clusters, and find that the quality of fit is generally at least as good as that for the surface brightness profiles of King. This model can be used for convenient computation of the dynamics and evolution of globular and nuclear star clusters.

  5. Molecular dynamics modelling of EGCG clusters on ceramide bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Yeo, Jingjie; Cheng, Yuan; Li, Weifeng; Zhang, Yong-Wei [Institute of High Performance Computing, A*STAR, 138632 (Singapore)

    2015-12-31

    A novel method of atomistic modelling and characterization of both pure ceramide and mixed lipid bilayers is being developed, using only the General Amber ForceField. Lipid bilayers modelled as pure ceramides adopt hexagonal packing after equilibration, and the area per lipid and bilayer thickness are consistent with previously reported theoretical results. Mixed lipid bilayers are modelled as a combination of ceramides, cholesterol, and free fatty acids. This model is shown to be stable after equilibration. Green tea extract, also known as epigallocatechin-3-gallate, is introduced as a spherical cluster on the surface of the mixed lipid bilayer. It is demonstrated that the cluster is able to bind to the bilayers as a cluster without diffusing into the surrounding water.

  6. Multi-scale Clustering of Points Synthetically Considering Lines and Polygons Distribution

    Directory of Open Access Journals (Sweden)

    YU Li

    2015-10-01

    Full Text Available Considering the complexity and discontinuity of spatial data distribution, a clustering algorithm of points was proposed. To accurately identify and express the spatial correlation among points,lines and polygons, a Voronoi diagram that is generated by all spatial features is introduced. According to the distribution characteristics of point's position, an area threshold used to control clustering granularity was calculated. Meanwhile, judging scale convergence by constant area threshold, the algorithm classifies spatial features based on multi-scale, with an O(n log n running time.Results indicate that spatial scale converges self-adaptively according with distribution of points.Without the custom parameters, the algorithm capable to discover arbitrary shape clusters which be bound by lines and polygons, and is robust for outliers.

  7. Phenotype Clustering of Breast Epithelial Cells in Confocal Imagesbased on Nuclear Protein Distribution Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Long, Fuhui; Peng, Hanchuan; Sudar, Damir; Levievre, Sophie A.; Knowles, David W.

    2006-09-05

    Background: The distribution of the chromatin-associatedproteins plays a key role in directing nuclear function. Previously, wedeveloped an image-based method to quantify the nuclear distributions ofproteins and showed that these distributions depended on the phenotype ofhuman mammary epithelial cells. Here we describe a method that creates ahierarchical tree of the given cell phenotypes and calculates thestatistical significance between them, based on the clustering analysisof nuclear protein distributions. Results: Nuclear distributions ofnuclear mitotic apparatus protein were previously obtained fornon-neoplastic S1 and malignant T4-2 human mammary epithelial cellscultured for up to 12 days. Cell phenotype was defined as S1 or T4-2 andthe number of days in cultured. A probabilistic ensemble approach wasused to define a set of consensus clusters from the results of multipletraditional cluster analysis techniques applied to the nucleardistribution data. Cluster histograms were constructed to show how cellsin any one phenotype were distributed across the consensus clusters.Grouping various phenotypes allowed us to build phenotype trees andcalculate the statistical difference between each group. The resultsshowed that non-neoplastic S1 cells could be distinguished from malignantT4-2 cells with 94.19 percent accuracy; that proliferating S1 cells couldbe distinguished from differentiated S1 cells with 92.86 percentaccuracy; and showed no significant difference between the variousphenotypes of T4-2 cells corresponding to increasing tumor sizes.Conclusion: This work presents a cluster analysis method that canidentify significant cell phenotypes, based on the nuclear distributionof specific proteins, with high accuracy.

  8. Income dynamics with a stationary double Pareto distribution.

    Science.gov (United States)

    Toda, Alexis Akira

    2011-04-01

    Once controlled for the trend, the distribution of personal income appears to be double Pareto, a distribution that obeys the power law exactly in both the upper and the lower tails. I propose a model of income dynamics with a stationary distribution that is consistent with this fact. Using US male wage data for 1970-1993, I estimate the power law exponent in two ways--(i) from each cross section, assuming that the distribution has converged to the stationary distribution, and (ii) from a panel directly estimating the parameters of the income dynamics model--and obtain the same value of 8.4.

  9. Electric Vehicle (EV) Charging Management with Dynamic Distribution System Tariff

    DEFF Research Database (Denmark)

    O'Connell, Niamh; Wu, Qiuwei; Østergaard, Jacob

    2011-01-01

    An electric vehicle (EV) charging schedule algorithm was proposed in this paper in order to charge EVs to meet EV users’ driving needs with the minimum EV charging cost and respect the local distribution system constraints. A day-ahead dynamic distribution system tariff scheme was proposed to avoid...... congestions in local distribution systems from the day-ahead planning perspective. Locational marginal pricing method was used to determine the dynamic distribution system tariff based on predicted day-ahead spot prices and predicted charging behaviors. Distribution grids of the Bornholm power system were...... used to carry out case studies to illustrate the proposed EV charging schedule algorithm....

  10. Foot and mouth disease in Zambia: Spatial and temporal distributions of outbreaks, assessment of clusters and implications for control

    Directory of Open Access Journals (Sweden)

    Yona Sinkala

    2014-04-01

    Full Text Available Zambia has been experiencing low livestock productivity as well as trade restrictions owing to the occurrence of foot and mouth disease (FMD, but little is known about the epidemiology of the disease in these endemic settings. The fundamental questions relate to the spatio-temporal distribution of FMD cases and what determines their occurrence. A retrospective review of FMD cases in Zambia from 1981 to 2012 was conducted using geographical information systems and the SaTScan software package. Information was collected from peer-reviewed journal articles, conference proceedings, laboratory reports, unpublished scientific reports and grey literature. A space–time permutation probability model using a varying time window of one year was used to scan for areas with high infection rates. The spatial scan statistic detected a significant purely spatial cluster around the Mbala–Isoka area between 2009 and 2012, with secondary clusters in Sesheke–Kazungula in 2007 and 2008, the Kafue flats in 2004 and 2005 and Livingstone in 2012. This study provides evidence of the existence of statistically significant FMD clusters and an increase in occurrence in Zambia between 2004 and 2012. The identified clusters agree with areas known to be at high risk of FMD. The FMD virus transmission dynamics and the heterogeneous variability in risk within these locations may need further investigation.

  11. Foot and mouth disease in Zambia: spatial and temporal distributions of outbreaks, assessment of clusters and implications for control.

    Science.gov (United States)

    Sinkala, Yona; Simuunza, Martin; Muma, John B; Pfeiffer, Dirk U; Kasanga, Christopher J; Mweene, Aaron

    2014-04-23

    Zambia has been experiencing low livestock productivity as well as trade restrictions owing to the occurrence of foot and mouth disease (FMD), but little is known about the epidemiology of the disease in these endemic settings. The fundamental questions relate to the spatio-temporal distribution of FMD cases and what determines their occurrence. A retrospective review of FMD cases in Zambia from 1981 to 2012 was conducted using geographical information systems and the SaTScan software package. Information was collected from peer-reviewed journal articles, conference proceedings, laboratory reports, unpublished scientific reports and grey literature. A space-time permutation probability model using a varying time window of one year was used to scan for areas with high infection rates. The spatial scan statistic detected a significant purely spatial cluster around the Mbala-Isoka area between 2009 and 2012, with secondary clusters in Sesheke-Kazungula in 2007 and 2008, the Kafue flats in 2004 and 2005 and Livingstone in 2012. This study provides evidence of the existence of statistically significant FMD clusters and an increase in occurrence in Zambia between 2004 and 2012. The identified clusters agree with areas known to be at high risk of FMD. The FMD virus transmission dynamics and the heterogeneous variability in risk within these locations may need further investigation.

  12. Distribution of histaminergic neuronal cluster in the rat and mouse hypothalamus.

    Science.gov (United States)

    Moriwaki, Chinatsu; Chiba, Seiichi; Wei, Huixing; Aosa, Taishi; Kitamura, Hirokazu; Ina, Keisuke; Shibata, Hirotaka; Fujikura, Yoshihisa

    2015-10-01

    Histidine decarboxylase (HDC) catalyzes the biosynthesis of histamine from L-histidine and is expressed throughout the mammalian nervous system by histaminergic neurons. Histaminergic neurons arise in the posterior mesencephalon during the early embryonic period and gradually develop into two histaminergic substreams around the lateral area of the posterior hypothalamus and the more anterior peri-cerebral aqueduct area before finally forming an adult-like pattern comprising five neuronal clusters, E1, E2, E3, E4, and E5, at the postnatal stage. This distribution of histaminergic neuronal clusters in the rat hypothalamus appears to be a consequence of neuronal development and reflects the functional differentiation within each neuronal cluster. However, the close linkage between the locations of histaminergic neuronal clusters and their physiological functions has yet to be fully elucidated because of the sparse information regarding the location and orientation of each histaminergic neuronal clusters in the hypothalamus of rats and mice. To clarify the distribution of the five-histaminergic neuronal clusters more clearly, we performed an immunohistochemical study using the anti-HDC antibody on serial sections of the rat hypothalamus according to the brain maps of rat and mouse. Our results confirmed that the HDC-immunoreactive (HDCi) neuronal clusters in the hypothalamus of rats and mice are observed in the ventrolateral part of the most posterior hypothalamus (E1), ventrolateral part of the posterior hypothalamus (E2), ventromedial part from the medial to the posterior hypothalamus (E3), periventricular part from the anterior to the medial hypothalamus (E4), and diffusely extended part of the more dorsal and almost entire hypothalamus (E5). The stereological estimation of the total number of HDCi neurons of each clusters revealed the larger amount of the rat than the mouse. The characterization of histaminergic neuronal clusters in the hypothalamus of rats and

  13. A dynamic lattice searching method with rotation operation for optimization of large clusters

    International Nuclear Information System (INIS)

    Wu Xia; Cai Wensheng; Shao Xueguang

    2009-01-01

    Global optimization of large clusters has been a difficult task, though much effort has been paid and many efficient methods have been proposed. During our works, a rotation operation (RO) is designed to realize the structural transformation from decahedra to icosahedra for the optimization of large clusters, by rotating the atoms below the center atom with a definite degree around the fivefold axis. Based on the RO, a development of the previous dynamic lattice searching with constructed core (DLSc), named as DLSc-RO, is presented. With an investigation of the method for the optimization of Lennard-Jones (LJ) clusters, i.e., LJ 500 , LJ 561 , LJ 600 , LJ 665-667 , LJ 670 , LJ 685 , and LJ 923 , Morse clusters, silver clusters by Gupta potential, and aluminum clusters by NP-B potential, it was found that both the global minima with icosahedral and decahedral motifs can be obtained, and the method is proved to be efficient and universal.

  14. Effect of Policy Analysis on Indonesia’s Maritime Cluster Development Using System Dynamics Modeling

    Science.gov (United States)

    Nursyamsi, A.; Moeis, A. O.; Komarudin

    2018-03-01

    As an archipelago with two third of its territory consist of water, Indonesia should address more attention to its maritime industry development. One of the catalyst to fasten the maritime industry growth is by developing a maritime cluster. The purpose of this research is to gain understanding of the effect if Indonesia implement maritime cluster policy to the growth of maritime economic and its role to enhance the maritime cluster performance, hence enhancing Indonesia’s maritime industry as well. The result of the constructed system dynamic model simulation shows that with the effect of maritime cluster, the growth of employment rate and maritime economic is much bigger that the business as usual case exponentially. The result implies that the government should act fast to form a legitimate cluster maritime organizer institution so that there will be a synergize, sustainable, and positive maritime cluster environment that will benefit the performance of Indonesia’s maritime industry.

  15. Clustering analysis of water distribution systems: identifying critical components and community impacts.

    Science.gov (United States)

    Diao, K; Farmani, R; Fu, G; Astaraie-Imani, M; Ward, S; Butler, D

    2014-01-01

    Large water distribution systems (WDSs) are networks with both topological and behavioural complexity. Thereby, it is usually difficult to identify the key features of the properties of the system, and subsequently all the critical components within the system for a given purpose of design or control. One way is, however, to more explicitly visualize the network structure and interactions between components by dividing a WDS into a number of clusters (subsystems). Accordingly, this paper introduces a clustering strategy that decomposes WDSs into clusters with stronger internal connections than external connections. The detected cluster layout is very similar to the community structure of the served urban area. As WDSs may expand along with urban development in a community-by-community manner, the correspondingly formed distribution clusters may reveal some crucial configurations of WDSs. For verification, the method is applied to identify all the critical links during firefighting for the vulnerability analysis of a real-world WDS. Moreover, both the most critical pipes and clusters are addressed, given the consequences of pipe failure. Compared with the enumeration method, the method used in this study identifies the same group of the most critical components, and provides similar criticality prioritizations of them in a more computationally efficient time.

  16. Superferromagnetism in mechanically alloyed fcc Fe23Cu77 with bimodal cluster size distribution

    International Nuclear Information System (INIS)

    Silva, N J O; Amaral, J S; Amaral, V S; Costa, B F O; Le Caer, G

    2009-01-01

    Magnetic measurements, x-ray diffraction and Moessbauer spectroscopy were used to characterize a nanostructured fcc Fe 23 Cu 77 at.% alloy prepared by high-energy ball-milling, addressing in particular the effect of clustering on the nature of the interacting magnetic entities. The interpretation of magnetization measurements leads to the conclusion that grains, whose mean size is ∼16 nm, contain two populations of magnetic Fe-rich nanoclusters with a bimodal size distribution. These two sets of clusters contain about 14 and 400 Fe atoms and have magnetic moments of 30 μ B and 860 μ B , respectively. The inter-cluster ferromagnetic interactions that lead to superferromagnetism with a Curie temperature T C ∼220 K can be described by a mean field determined by the smaller clusters only, which account for 90% of the magnetization.

  17. K-means clustering for optimal partitioning and dynamic load balancing of parallel hierarchical N-body simulations

    International Nuclear Information System (INIS)

    Marzouk, Youssef M.; Ghoniem, Ahmed F.

    2005-01-01

    A number of complex physical problems can be approached through N-body simulation, from fluid flow at high Reynolds number to gravitational astrophysics and molecular dynamics. In all these applications, direct summation is prohibitively expensive for large N and thus hierarchical methods are employed for fast summation. This work introduces new algorithms, based on k-means clustering, for partitioning parallel hierarchical N-body interactions. We demonstrate that the number of particle-cluster interactions and the order at which they are performed are directly affected by partition geometry. Weighted k-means partitions minimize the sum of clusters' second moments and create well-localized domains, and thus reduce the computational cost of N-body approximations by enabling the use of lower-order approximations and fewer cells. We also introduce compatible techniques for dynamic load balancing, including adaptive scaling of cluster volumes and adaptive redistribution of cluster centroids. We demonstrate the performance of these algorithms by constructing a parallel treecode for vortex particle simulations, based on the serial variable-order Cartesian code developed by Lindsay and Krasny [Journal of Computational Physics 172 (2) (2001) 879-907]. The method is applied to vortex simulations of a transverse jet. Results show outstanding parallel efficiencies even at high concurrencies, with velocity evaluation errors maintained at or below their serial values; on a realistic distribution of 1.2 million vortex particles, we observe a parallel efficiency of 98% on 1024 processors. Excellent load balance is achieved even in the face of several obstacles, such as an irregular, time-evolving particle distribution containing a range of length scales and the continual introduction of new vortex particles throughout the domain. Moreover, results suggest that k-means yields a more efficient partition of the domain than a global oct-tree

  18. Location and Size Planning of Distributed Photovoltaic Generation in Distribution network System Based on K-means Clustering Analysis

    Science.gov (United States)

    Lu, Siqi; Wang, Xiaorong; Wu, Junyong

    2018-01-01

    The paper presents a method to generate the planning scenarios, which is based on K-means clustering analysis algorithm driven by data, for the location and size planning of distributed photovoltaic (PV) units in the network. Taken the power losses of the network, the installation and maintenance costs of distributed PV, the profit of distributed PV and the voltage offset as objectives and the locations and sizes of distributed PV as decision variables, Pareto optimal front is obtained through the self-adaptive genetic algorithm (GA) and solutions are ranked by a method called technique for order preference by similarity to an ideal solution (TOPSIS). Finally, select the planning schemes at the top of the ranking list based on different planning emphasis after the analysis in detail. The proposed method is applied to a 10-kV distribution network in Gansu Province, China and the results are discussed.

  19. Distributed Coordination of Islanded Microgrid Clusters Using a Two-layer Intermittent Communication Network

    DEFF Research Database (Denmark)

    Lu, Xiaoqing; Lai, Jingang; Yu, Xinghuo

    2018-01-01

    This paper proposes a distributed hierarchical cooperative (DHC) control strategy for a cluster of islanded microgrids (MGs) with intermittent communciation, which can regulate the frequency/voltage of all distributed generators (DGs) within each MG as well as ensure the active/reactive power...... sharing among MGs. A droop-based distributed secondary control (DSC) scheme and a distributed tertiary control (DTC) scheme are presented based on the iterative learning mechanics, by which the control inputs are merely updated at the end of each round of iteration, and thus each DG only needs to share...... in each MG. The effectiveness of the proposed control methodology is verified by the simulation of an AC MG cluster in Simulink/SimPowerSystems....

  20. A Gloss Composition and Context Clustering Based Distributed Word Sense Representation Model

    Directory of Open Access Journals (Sweden)

    Tao Chen

    2015-08-01

    Full Text Available In recent years, there has been an increasing interest in learning a distributed representation of word sense. Traditional context clustering based models usually require careful tuning of model parameters, and typically perform worse on infrequent word senses. This paper presents a novel approach which addresses these limitations by first initializing the word sense embeddings through learning sentence-level embeddings from WordNet glosses using a convolutional neural networks. The initialized word sense embeddings are used by a context clustering based model to generate the distributed representations of word senses. Our learned representations outperform the publicly available embeddings on half of the metrics in the word similarity task, 6 out of 13 sub tasks in the analogical reasoning task, and gives the best overall accuracy in the word sense effect classification task, which shows the effectiveness of our proposed distributed distribution learning model.

  1. Mass and galaxy distributions of four massive galaxy clusters from Dark Energy Survey Science Verification data

    Science.gov (United States)

    Melchior, P.; Suchyta, E.; Huff, E.; Hirsch, M.; Kacprzak, T.; Rykoff, E.; Gruen, D.; Armstrong, R.; Bacon, D.; Bechtol, K.; Bernstein, G. M.; Bridle, S.; Clampitt, J.; Honscheid, K.; Jain, B.; Jouvel, S.; Krause, E.; Lin, H.; MacCrann, N.; Patton, K.; Plazas, A.; Rowe, B.; Vikram, V.; Wilcox, H.; Young, J.; Zuntz, J.; Abbott, T.; Abdalla, F. B.; Allam, S. S.; Banerji, M.; Bernstein, J. P.; Bernstein, R. A.; Bertin, E.; Buckley-Geer, E.; Burke, D. L.; Castander, F. J.; da Costa, L. N.; Cunha, C. E.; Depoy, D. L.; Desai, S.; Diehl, H. T.; Doel, P.; Estrada, J.; Evrard, A. E.; Neto, A. Fausti; Fernandez, E.; Finley, D. A.; Flaugher, B.; Frieman, J. A.; Gaztanaga, E.; Gerdes, D.; Gruendl, R. A.; Gutierrez, G. R.; Jarvis, M.; Karliner, I.; Kent, S.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Maia, M. A. G.; Makler, M.; Marriner, J.; Marshall, J. L.; Merritt, K. W.; Miller, C. J.; Miquel, R.; Mohr, J.; Neilsen, E.; Nichol, R. C.; Nord, B. D.; Reil, K.; Roe, N. A.; Roodman, A.; Sako, M.; Sanchez, E.; Santiago, B. X.; Schindler, R.; Schubnell, M.; Sevilla-Noarbe, I.; Sheldon, E.; Smith, C.; Soares-Santos, M.; Swanson, M. E. C.; Sypniewski, A. J.; Tarle, G.; Thaler, J.; Thomas, D.; Tucker, D. L.; Walker, A.; Wechsler, R.; Weller, J.; Wester, W.

    2015-05-01

    We measure the weak lensing masses and galaxy distributions of four massive galaxy clusters observed during the Science Verification phase of the Dark Energy Survey (DES). This pathfinder study is meant to (1) validate the Dark Energy Camera (DECam) imager for the task of measuring weak lensing shapes, and (2) utilize DECam's large field of view to map out the clusters and their environments over 90 arcmin. We conduct a series of rigorous tests on astrometry, photometry, image quality, point spread function (PSF) modelling, and shear measurement accuracy to single out flaws in the data and also to identify the optimal data processing steps and parameters. We find Science Verification data from DECam to be suitable for the lensing analysis described in this paper. The PSF is generally well behaved, but the modelling is rendered difficult by a flux-dependent PSF width and ellipticity. We employ photometric redshifts to distinguish between foreground and background galaxies, and a red-sequence cluster finder to provide cluster richness estimates and cluster-galaxy distributions. By fitting Navarro-Frenk-White profiles to the clusters in this study, we determine weak lensing masses that are in agreement with previous work. For Abell 3261, we provide the first estimates of redshift, weak lensing mass, and richness. In addition, the cluster-galaxy distributions indicate the presence of filamentary structures attached to 1E 0657-56 and RXC J2248.7-4431, stretching out as far as 1°(approximately 20 Mpc), showcasing the potential of DECam and DES for detailed studies of degree-scale features on the sky.

  2. Mass and galaxy distributions of four massive galaxy clusters from Dark Energy Survey Science Verification data

    Energy Technology Data Exchange (ETDEWEB)

    Melchior, P.; Suchyta, E.; Huff, E.; Hirsch, M.; Kacprzak, T.; Rykoff, E.; Gruen, D.; Armstrong, R.; Bacon, D.; Bechtol, K.; Bernstein, G. M.; Bridle, S.; Clampitt, J.; Honscheid, K.; Jain, B.; Jouvel, S.; Krause, E.; Lin, H.; MacCrann, N.; Patton, K.; Plazas, A.; Rowe, B.; Vikram, V.; Wilcox, H.; Young, J.; Zuntz, J.; Abbott, T.; Abdalla, F. B.; Allam, S. S.; Banerji, M.; Bernstein, J. P.; Bernstein, R. A.; Bertin, E.; Buckley-Geer, E.; Burke, D. L.; Castander, F. J.; da Costa, L. N.; Cunha, C. E.; Depoy, D. L.; Desai, S.; Diehl, H. T.; Doel, P.; Estrada, J.; Evrard, A. E.; Neto, A. F.; Fernandez, E.; Finley, D. A.; Flaugher, B.; Frieman, J. A.; Gaztanaga, E.; Gerdes, D.; Gruendl, R. A.; Gutierrez, G. R.; Jarvis, M.; Karliner, I.; Kent, S.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Maia, M. A. G.; Makler, M.; Marriner, J.; Marshall, J. L.; Merritt, K. W.; Miller, C. J.; Miquel, R.; Mohr, J.; Neilsen, E.; Nichol, R. C.; Nord, B. D.; Reil, K.; Roe, N. A.; Roodman, A.; Sako, M.; Sanchez, E.; Santiago, B. X.; Schindler, R.; Schubnell, M.; Sevilla-Noarbe, I.; Sheldon, E.; Smith, C.; Soares-Santos, M.; Swanson, M. E. C.; Sypniewski, A. J.; Tarle, G.; Thaler, J.; Thomas, D.; Tucker, D. L.; Walker, A.; Wechsler, R.; Weller, J.; Wester, W.

    2015-03-31

    We measure the weak-lensing masses and galaxy distributions of four massive galaxy clusters observed during the Science Verification phase of the Dark Energy Survey. This pathfinder study is meant to 1) validate the DECam imager for the task of measuring weak-lensing shapes, and 2) utilize DECam's large field of view to map out the clusters and their environments over 90 arcmin. We conduct a series of rigorous tests on astrometry, photometry, image quality, PSF modeling, and shear measurement accuracy to single out flaws in the data and also to identify the optimal data processing steps and parameters. We find Science Verification data from DECam to be suitable for the lensing analysis described in this paper. The PSF is generally well-behaved, but the modeling is rendered difficult by a flux-dependent PSF width and ellipticity. We employ photometric redshifts to distinguish between foreground and background galaxies, and a red-sequence cluster finder to provide cluster richness estimates and cluster-galaxy distributions. By fitting NFW profiles to the clusters in this study, we determine weak-lensing masses that are in agreement with previous work. For Abell 3261, we provide the first estimates of redshift, weak-lensing mass, and richness. In addition, the cluster-galaxy distributions indicate the presence of filamentary structures attached to 1E 0657-56 and RXC J2248.7-4431, stretching out as far as 1 degree (approximately 20 Mpc), showcasing the potential of DECam and DES for detailed studies of degree-scale features on the sky.

  3. Giant luminous arcs from lensing: determination of the mass distribution inside distant cluster cores

    International Nuclear Information System (INIS)

    Hammer, F.; Rigaut, F.

    1989-01-01

    The observations of giant luminous arcs are used in the context of the gravitational lensing theory, to investigate the distribution of the deflecting matter, usually situated in the cores of distant clusters. Analytic equations of the caustic curves are presented for a multi-point mass model, which roughly accounts for the observed arc properties. A more general lensing model is introduced, where the lensing objects (galaxies, groups and clusters of galaxies) are extended and follow the r 1/4 law. Numerical simulations reproduce pixel by pixel all the gravitational images, including the arcs, found in the cores of the A 370 and CI2244-02 clusters. They are consistent with the use of the observations of luminous matter and X-ray emitting matter as a tracer of the total mass distribution

  4. Giant luminous arcs from lensing: determination of the mass distribution inside distant cluster cores

    Energy Technology Data Exchange (ETDEWEB)

    Hammer, F.; Rigaut, F. (Observatoire de Paris, Section de Meudon, 92 (FR))

    1989-12-01

    The observations of giant luminous arcs are used in the context of the gravitational lensing theory, to investigate the distribution of the deflecting matter, usually situated in the cores of distant clusters. Analytic equations of the caustic curves are presented for a multi-point mass model, which roughly accounts for the observed arc properties. A more general lensing model is introduced, where the lensing objects (galaxies, groups and clusters of galaxies) are extended and follow the r{sup 1/4} law. Numerical simulations reproduce pixel by pixel all the gravitational images, including the arcs, found in the cores of the A 370 and CI2244-02 clusters. They are consistent with the use of the observations of luminous matter and X-ray emitting matter as a tracer of the total mass distribution.

  5. Towards the Availability of the Distributed Cluster Rendering System: Automatic Modeling and Verification

    DEFF Research Database (Denmark)

    Wang, Kemin; Jiang, Zhengtao; Wang, Yongbin

    2012-01-01

    In this study, we proposed a Continuous Time Markov Chain Model towards the availability of n-node clusters of Distributed Rendering System. It's an infinite one, we formalized it, based on the model, we implemented a software, which can automatically model with PRISM language. With the tool, whe...

  6. Fragmentation dynamics of ionized neon clusters (Ne(n), n=3-14) embedded in helium nanodroplets.

    Science.gov (United States)

    Bonhommeau, David; Halberstadt, Nadine; Viel, Alexandra

    2006-01-14

    We report a theoretical study of the nonadiabatic fragmentation dynamics of ionized neon clusters embedded in helium nanodroplets for cluster sizes up to n=14 atoms. The dynamics of the neon atoms is modeled using the molecular dynamics with quantum transitions method of Tully [J. Chem. Phys. 93, 1061 (1990)] with the nuclei treated classically and transitions between electronic states quantum mechanically. The potential-energy surfaces are derived from a diatomics-in-molecules model to which induced dipole-induced dipole interactions are added. The effect of the spin-orbit interaction is also discussed. The helium environment is modeled by a friction force acting on charged atoms whose speed exceeds the critical Landau velocity. The dependence of the fragment size distribution on the friction strength and on the initial nanodroplet size is investigated. By comparing with the available experimental data obtained for Ne3+ and Ne4+, a reasonable value for the friction coefficient, the only parameter of the model, is deduced. This value is then used to predict the effect of the helium environment on the dissociation dynamics of larger neon clusters, n=5-14. The results show stabilization of larger fragments than in the gas phase, but fragmentation is not completely caged. In addition, two types of dynamics are characterized for Ne4+: fast and explosive, therefore leaving no time for friction to cool down the process when dynamics starts on one of the highest electronic states, and slower, therefore leading to some stabilization by helium when it starts on one of the lowest electronic states.

  7. Probing surface distributions of α clusters in 20Ne via α -transfer reaction

    Science.gov (United States)

    Fukui, Tokuro; Taniguchi, Yasutaka; Suhara, Tadahiro; Kanada-En'yo, Yoshiko; Ogata, Kazuyuki

    2016-03-01

    Background: Direct evidence of the α -cluster manifestation in bound states has not been obtained yet, although a number of experimental studies were carried out to extract the information of the clustering. In particular in conventional analyses of α -transfer reactions, there exist a few significant problems on reaction models, which are insufficient to qualitatively discuss the cluster structure. Purpose: We aim to verify the manifestation of the α -cluster structure from observables. As the first application, we plan to extract the spatial information of the cluster structure of the 20Ne nucleus in its ground state through the cross section of the α -transfer reaction 16O(6Li,d )20Ne. Methods: For the analysis of the transfer reaction, we work with the coupled-channel Born approximation (CCBA) approach, in which the breakup effect of 6Li is explicitly taken into account by means of the continuum-discretized coupled-channel method based on the three-body α +d +16O model. The two methods are adopted to calculate the overlap function between 20Ne and α +16O ; one is the microscopic cluster model (MCM) with the generator coordinate method, and the other is the phenomenological two-body potential model (PM). Results: We show that the CCBA calculation with the MCM wave function gives a significant improvement of the theoretical result on the angular distribution of the transfer cross section, which is consistent with the experimental data. Employing the PM, it is discussed which region of the cluster wave function is probed on the transfer cross section. Conclusions: It is found that the surface region of the cluster wave function is sensitive to the cross section. The present work is situated as the first step in obtaining important information to systematically investigate the cluster structure.

  8. Analysis of the complex interferometry diagnostics applicability to deuterium clusters spatial density distribution measurements

    International Nuclear Information System (INIS)

    Martinkova, M.; Kalal, M.; Yong Joo Rhee

    2010-01-01

    Complete text of publication follows. In recent years interactions of high-intensity femtosecond lasers with deuterium clusters leading to Coulomb explosions and subsequent production of fusion neutrons attracted considerable attention due to their importance for inertial confinement fusion research and relevant material studies. Already created theoretical models still do not explain all features of laser-clusters interactions. From experiments performed it became clear that in order to maximize the neutron yield, finding a dependence of clusters size and especially their spatial distribution on experimental conditions becomes crucial. Identifying a suitable diagnostics to measure the deuterium clusters spatial distributions experimentally thus became an important task. In recent years, in order to repeat the fusion neutron production from Coulomb explosions of deuterium clusters, successful series of experiments were performed in the Laboratory of Quantum Optics in KAERI using the Ti:Sapphire laser system (30 fs, I > 10 16 W/cm 2 ). In our contribution results of a feasibility study of deuterium clusters spatial density distribution measurements performed by complex interferometry will be presented. It will be demonstrated that this particular diagnostics features an excellent suppression of detrimental effects introduced by diagnostic beam lower quality as well as by imperfections of optical components (including misalignment of the interferometer). For the purpose of this feasibility study close-to-reality computer generated interferograms were created based on relevant experimental data obtained in KAERI using their Ti:Sapphire laser (30 fs, I > 10 16 W/cm 2 ) and cryogenic system. These simulated interferograms included an effect of a small density perturbations caused by generated clusters in their presumed most likely regions of appearance. Comparison of the reconstructed phase-shifts with the undisturbed ones was made and found suitable from the point of

  9. Observation of dynamic equilibrium cluster phase in nanoparticle-polymer system

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Sugam, E-mail: sugam@barc.gov.in; Mehan, S.; Aswal, V. K. [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400094 (India); Schwein, R. [Institut Laue-Langevin, DS/LSS, 6 rue Jules Horowitz, F-38042 Grenoble Cedex 9 (France)

    2016-05-23

    Small-angle neutron scattering (SANS) and dynamic light scattering (DLS) have been used to investigate the existence of a cluster phase in a nanoparticle-polymer system. The nanoparticle-polymer system shows an interesting reentrant phase behavior where the charge stabilized silica nanoparticles undergo particle clustering and back to individual nanoparticles as a function of polymer concentration. This kind of phase behavior is believed to be directed by opposing attractive and repulsive interactions present in the system. The phase behavior shows two narrow regions of polymer concentration immediately before and after the two-phase formation indicating the possibility of the existence of some equilibrium clusters. DLS results show a much higher size of particles than individuals in these two regions which remains unchanged even after dilution. The SANS data show the evolution of attraction with increased volume fraction of the particles supporting the dynamic nature of these clusters.

  10. Observation of dynamic equilibrium cluster phase in nanoparticle-polymer system

    International Nuclear Information System (INIS)

    Kumar, Sugam; Mehan, S.; Aswal, V. K.; Schwein, R.

    2016-01-01

    Small-angle neutron scattering (SANS) and dynamic light scattering (DLS) have been used to investigate the existence of a cluster phase in a nanoparticle-polymer system. The nanoparticle-polymer system shows an interesting reentrant phase behavior where the charge stabilized silica nanoparticles undergo particle clustering and back to individual nanoparticles as a function of polymer concentration. This kind of phase behavior is believed to be directed by opposing attractive and repulsive interactions present in the system. The phase behavior shows two narrow regions of polymer concentration immediately before and after the two-phase formation indicating the possibility of the existence of some equilibrium clusters. DLS results show a much higher size of particles than individuals in these two regions which remains unchanged even after dilution. The SANS data show the evolution of attraction with increased volume fraction of the particles supporting the dynamic nature of these clusters.

  11. Observation of dynamic equilibrium cluster phase in nanoparticle-polymer system

    Science.gov (United States)

    Kumar, Sugam; Mehan, S.; Aswal, V. K.; Schwein, R.

    2016-05-01

    Small-angle neutron scattering (SANS) and dynamic light scattering (DLS) have been used to investigate the existence of a cluster phase in a nanoparticle-polymer system. The nanoparticle-polymer system shows an interesting reentrant phase behavior where the charge stabilized silica nanoparticles undergo particle clustering and back to individual nanoparticles as a function of polymer concentration. This kind of phase behavior is believed to be directed by opposing attractive and repulsive interactions present in the system. The phase behavior shows two narrow regions of polymer concentration immediately before and after the two-phase formation indicating the possibility of the existence of some equilibrium clusters. DLS results show a much higher size of particles than individuals in these two regions which remains unchanged even after dilution. The SANS data show the evolution of attraction with increased volume fraction of the particles supporting the dynamic nature of these clusters.

  12. Dynamic Distributed Storage for Scaling Blockchains

    OpenAIRE

    Raman, Ravi Kiran; Varshney, Lav R.

    2017-01-01

    Blockchain uses the idea of storing transaction data in the form of a distributed ledger wherein each node in the network stores a current copy of the sequence of transactions in the form of a hash chain. This requirement of storing the entire ledger incurs a high storage cost that grows undesirably large for high transaction rates and large networks. In this work we use the ideas of secret key sharing, private key encryption, and distributed storage to design a coding scheme such that each n...

  13. Observing Distributed Computation. A Dynamic-Epistemic Approach

    DEFF Research Database (Denmark)

    Mardare, Radu Iulian

    2007-01-01

    R. Mardare. Observing Distributed Computation. A Dynamic-Epistemic Approach. In Proc. of the second Conference on Algebra and Coalgebra in Computer Science (CALCO2007), Lecture Notes in Computer Science 4624:379-393, Springer, 2007......R. Mardare. Observing Distributed Computation. A Dynamic-Epistemic Approach. In Proc. of the second Conference on Algebra and Coalgebra in Computer Science (CALCO2007), Lecture Notes in Computer Science 4624:379-393, Springer, 2007...

  14. The Wedding of Modified Dynamics and Non-Exotic Dark Matter in Galaxy Clusters

    Science.gov (United States)

    Famaey, B.; Angus, G. W.; Gentile, G.; Shan, H. Y.; Zhao, H. S.

    2008-04-01

    We summarize the status of Modified Newtonian Dynamics (MOND) in galaxy clusters. The observed acceleration is typically larger than the acceleration threshold of MOND in the central regions, implying that some dark matter is necessary to explain the mass discrepancy there. A plausible resolution of this issue is that the unseen mass in MOND is in the form of ordinary neutrinos with masses just below the experimentally detectable limit. In particular, we show that the lensing mass reconstructions of the rich clusters 1E0657-56 (the bullet cluster) and Cl0024+17 (the ring) do not pose a new challenge to this scenario. However, the mass discrepancy for cool X-ray emitting groups in which neutrinos cannot cluster pose a more serious problem, meaning that dark baryons could present a more satisfactory solution to the problem of unseen mass in MOND clusters.

  15. Modelling flow dynamics in water distribution networks using ...

    African Journals Online (AJOL)

    One such approach is the Artificial Neural Networks (ANNs) technique. The advantage of ANNs is that they are robust and can be used to model complex linear and non-linear systems without making implicit assumptions. ANNs can be trained to forecast flow dynamics in a water distribution network. Such flow dynamics ...

  16. Entry Times Distribution for Dynamical Balls on Metric Spaces

    Science.gov (United States)

    Haydn, N.; Yang, F.

    2017-04-01

    We show that the entry and return times for dynamical balls (Bowen balls) is exponential for systems that have an α -mixing invariant measure with certain regularities. We also show that systems modeled by Young's tower has exponential entry time distribution for dynamical balls. We also apply the results to conformal maps and expanding maps on the interval.

  17. Implementation of Parallel Dynamic Simulation on Shared-Memory vs. Distributed-Memory Environments

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Shuangshuang; Chen, Yousu; Wu, Di; Diao, Ruisheng; Huang, Zhenyu

    2015-12-09

    Power system dynamic simulation computes the system response to a sequence of large disturbance, such as sudden changes in generation or load, or a network short circuit followed by protective branch switching operation. It consists of a large set of differential and algebraic equations, which is computational intensive and challenging to solve using single-processor based dynamic simulation solution. High-performance computing (HPC) based parallel computing is a very promising technology to speed up the computation and facilitate the simulation process. This paper presents two different parallel implementations of power grid dynamic simulation using Open Multi-processing (OpenMP) on shared-memory platform, and Message Passing Interface (MPI) on distributed-memory clusters, respectively. The difference of the parallel simulation algorithms and architectures of the two HPC technologies are illustrated, and their performances for running parallel dynamic simulation are compared and demonstrated.

  18. Energy efficient distributed cluster head scheduling scheme for two tiered wireless sensor network

    Directory of Open Access Journals (Sweden)

    G. Kannan

    2015-07-01

    Full Text Available Wireless Sensor Network (WSN provides a significant contribution in the emerging fields such as ambient intelligence and ubiquitous computing. In WSN, optimization and load balancing of network resources are critical concern to provide the intelligence for long duration. Since clustering the sensor nodes can significantly enhance overall system scalability and energy efficiency this paper presents a distributed cluster head scheduling (DCHS algorithm to achieve the network longevity in WSN. The major novelty of this work is that the network is divided into primary and secondary tiers based on received signal strength indication of sensor nodes from the base station. The proposed DCHS supports for two tier WSN architecture and gives suggestion to elect the cluster head nodes and gateway nodes for both primary and secondary tiers. The DCHS mechanism satisfies an ideal distribution of the cluster head among the sensor nodes and avoids frequent selection of cluster head, based on Received Signal Strength Indication (RSSI and residual energy level of the sensor nodes. Since the RSSI is the key parameter for this paper, the practical experiment was conducted to measure RSSI value by using MSP430F149 processor and CC2500 transceiver. The measured RSSI values were given input to the event based simulator to test the DCHS mechanism. The real time experimental study validated the proposed scheme for various scenarios.

  19. Geographical Distribution and Cluster Detection of Childhood Leukemia in the Metropolitan Area of Guadalajara, Mexico.

    Science.gov (United States)

    Tlacuilo-Parra, Alberto; Garibaldi-Covarrubias, Roberto; Romo-Rubio, Hugo; Soto-Sumuano, Leonardo; Ruiz-Chávez, Carlos Fernando; Suárez-Arredondo, Mijail; Sánchez-Zubieta, Fernando; Gallegos-Castorena, Sergio

    2017-01-01

    Acute leukemia is the most common cancer in childhood. Analyzing the spatial distribution of acute leukemia may generate the identification of risk factors. To study the incidence rate of acute leukemia, its geographic distribution, and cluster detection in the metropolitan area of Guadalajara, Mexico. We included children under 15 years of age diagnosed with acute leukemia during the period 2010-2014 in the metropolitan area of Guadalajara. Each case was geo-referenced to street level to latitude and longitude coordinates using Quantum Geographic Information System (QGIS). Spatial clusters were found in the location of the acute leukemia cases applying the Density-Based Spatial Clustering of Applications with Noise (DBSCAN) algorithm with R statistical software. A total of 269 cases of leukemia were registered, 227 (84%) were acute lymphoblastic leukemia and 42 (16%) acute myeloblastic leukemia. The mean age was 6 ± 4 years. The mean incidence of acute leukemia was 6.44 cases/100,000 inhabitants: El Salto 10.12/100,000, Guadalajara 7.55/100,000, and Tlaquepaque 6.74/100,000. The DBSCAN found three clusters, all located within the municipality of Guadalajara. The incidence of acute leukemia in our population is higher than that in Canada and the USA. We found three spatial clusters of childhood acute lymphoblastic leukemia in the municipality of Guadalajara, suggesting the presence of local predisposing factors.

  20. DLTAP: A Network-efficient Scheduling Method for Distributed Deep Learning Workload in Containerized Cluster Environment

    Directory of Open Access Journals (Sweden)

    Qiao Wei

    2017-01-01

    Full Text Available Deep neural networks (DNNs have recently yielded strong results on a range of applications. Training these DNNs using a cluster of commodity machines is a promising approach since training is time consuming and compute-intensive. Furthermore, putting DNN tasks into containers of clusters would enable broader and easier deployment of DNN-based algorithms. Toward this end, this paper addresses the problem of scheduling DNN tasks in the containerized cluster environment. Efficiently scheduling data-parallel computation jobs like DNN over containerized clusters is critical for job performance, system throughput, and resource utilization. It becomes even more challenging with the complex workloads. We propose a scheduling method called Deep Learning Task Allocation Priority (DLTAP which performs scheduling decisions in a distributed manner, and each of scheduling decisions takes aggregation degree of parameter sever task and worker task into account, in particularly, to reduce cross-node network transmission traffic and, correspondingly, decrease the DNN training time. We evaluate the DLTAP scheduling method using a state-of-the-art distributed DNN training framework on 3 benchmarks. The results show that the proposed method can averagely reduce 12% cross-node network traffic, and decrease the DNN training time even with the cluster of low-end servers.

  1. On the projected mass distribution around galaxy clusters . A Lagrangian theory of harmonic power spectra

    Science.gov (United States)

    Codis, Sandrine; Gavazzi, Raphaël; Pichon, Christophe; Gouin, Céline

    2017-09-01

    Aims: Gravitational lensing allows us to quantify the angular distribution of the convergence field around clusters of galaxies to constrain their connectivity to the cosmic web. We describe the corresponding theory in Lagrangian space in which analytical results can be obtained by identifying clusters to peaks in the initial field. Methods: We derived the three-point Gaussian statistics of a two-dimensional (2D) field and its first and second derivatives. The formalism allowed us to study the statistics of the field in a shell around a central peak, in particular its multipolar decomposition. Results: The peak condition is shown to significantly remove power from the dipolar contribution and to modify the monopole and quadrupole. As expected, higher order multipoles are not significantly modified by the constraint. Analytical predictions are successfully checked against measurements in Gaussian random fields. The effect of substructures and radial weighting is shown to be small and does not change the qualitative picture.The non-linear evolution is shown to induce a non-linear bias of all multipoles proportional to the cluster mass. Conclusions: We predict the Gaussian and weakly non-Gaussian statistics of multipolar moments of a 2D field around a peak as a proxy for the azimuthal distribution of the convergence field around a cluster of galaxies. A quantitative estimate of this multipolar decomposition of the convergence field around clusters in numerical simulations of structure formation and in observations will be presented in two forthcoming papers.

  2. A clustering analysis of eddies' spatial distribution in the South China Sea

    Science.gov (United States)

    Yi, J.; Du, Y.; Wang, X.; He, Z.; Zhou, C.

    2013-02-01

    Spatial variation is important for studying the mesoscale eddies in the South China Sea (SCS). To investigate such spatial variations, this study made a clustering analysis on eddies' distribution using the K-means approach. Results showed that clustering tendency of anticyclonic eddies (AEs) and cyclonic eddies (CEs) were weak but not random, and the number of clusters were proved greater than four. Finer clustering results showed 10 regions where AEs densely populated and 6 regions for CEs in the SCS. Previous studies confirmed these partitions and possible generation mechanisms were related. Comparisons between AEs and CEs revealed that patterns of AE are relatively more aggregated than those of CE, and specific distinctions were summarized: (1) to the southwest of Luzon Island, AEs and CEs are generated spatially apart; AEs are likely located north of 14° N and closer to shore, while CEs are to the south and further offshore. (2) The central SCS and Nansha Trough are mostly dominated by AEs. (3) Along 112° E, clusters of AEs and CEs are located sequentially apart, and the pairs off Vietnam represent the dipole structures. (4) To the southwest of the Dongsha Islands, AEs are concentrated to the east of CEs. Overlaps of AEs and CEs in the northeastern and southern SCS were further examined considering seasonal variations. The northeastern overlap represented near-concentric distributions while the southern one was a mixed effect of seasonal variations, complex circulations and topography influences.

  3. clusters

    Indian Academy of Sciences (India)

    2017-09-27

    Sep 27, 2017 ... while CuCoNO, Co3NO, Cu3CoNO, Cu2Co3NO, Cu3Co3NO and Cu6CoNO clusters display stronger chemical stability. Magnetic and electronic properties are also discussed. The magnetic moment is affected by charge transfer and the spd hybridization. Keywords. CumConNO (m + n = 2–7) clusters; ...

  4. Dynamical Substructures of Galactic Globular Clusters III. NGC 7006

    Directory of Open Access Journals (Sweden)

    Jonghwan Rhee

    2005-12-01

    Full Text Available To study the effects of giant population on dynamical substructures of the central region of NGC 7006, we examine the radial variations of ellipticity and position angle on BV stellar photometry using ellipse fitting technique. Total variations of ellipticity and position angle lie in the range 0.02˜0.06 and -10° ˜ +90°, respectively, from the center out to three times the half light radius. Our ellipse fitting results, after removing giant populations, show that the apparent central dynamical substructures of NGC 7006 are mainly affected by red giant, horizontal branch stars. On the contrary, the contribution of light from subgiant stars to the inner dynamical substructure seems to be insignificant.

  5. Dynamics of the young LMC cluster NGC 1866

    Science.gov (United States)

    Fischer, Philippe; Welch, Douglas L.; Cote, Patrick; Mateo, Mario; Madore, Barry F.

    1992-01-01

    The 1.0-m telescope at Las Campanas was used to obtain V-band CCD images of the young LMC cluster NGC 1866 out to a projected radius of 100 pc. Radial velocities with a mean precision of 1.0 km/s were measured for 69 member supergiants using the echelle spectrograph on the 2.5-m telescope. The total cluster luminosity is 6.5 +/-0.3 x 10 exp 5 solar luminosities. A star-subtracted, median-filtered U frame was employed to determine photometric shape parameters. The stellar radial velocities indicate that NGC 1866 has a systemic velocity of 301.2 +/-1.0 km/s. A comparison of the derived values for NGC 1866 and the theoretical nu-0/sigma-0 - epsilon relationship indicates that the observed flattening is consistent with rotation. The quality of the fits for models with rotation is clearly superior to those without, and isotropic orbits agree best with the data in both cases.

  6. Self-diffusion dynamic behavior of atomic clusters on Re(0 0 0 1) surface

    Energy Technology Data Exchange (ETDEWEB)

    Liu Fusheng [Department of Applied Physics, Hunan University, Changsha 410082 (China); Hu Wangyu, E-mail: wangyuhu2001cn@yahoo.com.cn [Department of Applied Physics, Hunan University, Changsha 410082 (China); Deng Huiqiu; Luo Wenhua; Xiao Shifang [Department of Applied Physics, Hunan University, Changsha 410082 (China); Yang Jianyu [Department of Maths and Physics, Hunan Institute of Engineering, Xiangtan 411104 (China)

    2009-08-15

    Using molecular dynamics simulations and a modified analytic embedded atom potential, the self-diffusion dynamics of rhenium atomic clusters up to seven atoms on Re(0 0 0 1) surface have been studied in the temperature ranges from 600 K to 1900 K. The simulation time varies from 20 ns to 200 ns according to the cluster sizes and the temperature. The heptamer and trimer are more stable comparing to other neighboring non-compact clusters. The diffusion coefficients of clusters are derived from the mean square displacement of cluster's mass-center, and diffusion prefactors D{sub 0} and activation energies E{sub a} are derived from the Arrhenius relation. It is found that the Arrhenius relation of the adatom can be divided into two parts at different temperature range. The activation energy of clusters increases with the increasing of the atom number in clusters. The prefactor of the heptamer is 2-3 orders of magnitude higher than a usual prefactor because of a large number of nonequivalent diffusion processes. The trimer and heptamer are the nuclei at different temperature range according to the nucleation theory.

  7. On the ultrafast charge migration dynamics in isolated ionized halogen, chalcogen, pnicogen, and tetrel bonded clusters

    Energy Technology Data Exchange (ETDEWEB)

    Chandra, Sankhabrata; Rana, Bhaskar [Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore (India); Periyasamy, Ganga [Department of Chemistry, Central College Campus, Bangalore University, Bangalore (India); Bhattacharya, Atanu, E-mail: atanub@ipc.iisc.ernet.in [Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore (India)

    2016-06-15

    Highlights: • Attosecond charge migration following ionization. • Halogen, chalcogen, pnicogen, and tetrel bonds. • Density functional theory. • Linear combination of atomic orbitals (LCAO). - Abstract: Here we demonstrate, compare and contrast relaxation- and correlation-driven charge migration dynamics in halogen, chalcogen, pnicogen and tetrel bonded clusters, following their vertical ionization. For this work, we have selected different isolated A–X:NH{sub 3} clusters, where A represents F, Cl, CN and NH{sub 2} substituents and X features Cl, SH, PH{sub 2} and SiH{sub 3} to exhibit specific noncovalent bonding interaction. The charge migration dynamics in these clusters is studied using the density functional theory (DFT) with the wB97XD functional and the 6-31+G(d,p) basis set. Approximately 400–600 attosecond time scale is predicted for charge migration in (1:1) AX:NH{sub 3} complexes. Effects of basis set and intermolecular distance on the ultrafast charge migration dynamics through the halogen, chalcogen, pnicogen, and tetrel bonded clusters are also discussed. This is the first report on pure relaxation- and correlation-driven charge migration dynamics in chalcogen, pnicogen and tetrel bonded clusters.

  8. Statistics of matter distribution from halo dynamics

    International Nuclear Information System (INIS)

    Bonometto, S.A.; Borgani, S.; Persic, M.; Salucci, P.

    1990-01-01

    The galaxy-background correlation function at short distances is explored by means of the observed disk dynamics of spiral galaxies. Using both the sample of galaxies and the analytical method for dark-to-luminous mass decomposition from optical rotation curves presented by Persic and Salucci (1988, 1990), individual sizes and mean densities are worked out for 42 extended halos as functions of both the intensity and the gradient of the central velocity field. The statistics for the expected density enhancements within given distances from galactic centers shows simple properties which strongly tie galaxy-background and galaxy-galaxy correlation functions. 42 refs

  9. Fuzzy-Logic Based Distributed Energy-Efficient Clustering Algorithm for Wireless Sensor Networks.

    Science.gov (United States)

    Zhang, Ying; Wang, Jun; Han, Dezhi; Wu, Huafeng; Zhou, Rundong

    2017-07-03

    Due to the high-energy efficiency and scalability, the clustering routing algorithm has been widely used in wireless sensor networks (WSNs). In order to gather information more efficiently, each sensor node transmits data to its Cluster Head (CH) to which it belongs, by multi-hop communication. However, the multi-hop communication in the cluster brings the problem of excessive energy consumption of the relay nodes which are closer to the CH. These nodes' energy will be consumed more quickly than the farther nodes, which brings the negative influence on load balance for the whole networks. Therefore, we propose an energy-efficient distributed clustering algorithm based on fuzzy approach with non-uniform distribution (EEDCF). During CHs' election, we take nodes' energies, nodes' degree and neighbor nodes' residual energies into consideration as the input parameters. In addition, we take advantage of Takagi, Sugeno and Kang (TSK) fuzzy model instead of traditional method as our inference system to guarantee the quantitative analysis more reasonable. In our scheme, each sensor node calculates the probability of being as CH with the help of fuzzy inference system in a distributed way. The experimental results indicate EEDCF algorithm is better than some current representative methods in aspects of data transmission, energy consumption and lifetime of networks.

  10. Fuzzy-Logic Based Distributed Energy-Efficient Clustering Algorithm for Wireless Sensor Networks

    Science.gov (United States)

    Zhang, Ying; Wang, Jun; Han, Dezhi; Wu, Huafeng; Zhou, Rundong

    2017-01-01

    Due to the high-energy efficiency and scalability, the clustering routing algorithm has been widely used in wireless sensor networks (WSNs). In order to gather information more efficiently, each sensor node transmits data to its Cluster Head (CH) to which it belongs, by multi-hop communication. However, the multi-hop communication in the cluster brings the problem of excessive energy consumption of the relay nodes which are closer to the CH. These nodes’ energy will be consumed more quickly than the farther nodes, which brings the negative influence on load balance for the whole networks. Therefore, we propose an energy-efficient distributed clustering algorithm based on fuzzy approach with non-uniform distribution (EEDCF). During CHs’ election, we take nodes’ energies, nodes’ degree and neighbor nodes’ residual energies into consideration as the input parameters. In addition, we take advantage of Takagi, Sugeno and Kang (TSK) fuzzy model instead of traditional method as our inference system to guarantee the quantitative analysis more reasonable. In our scheme, each sensor node calculates the probability of being as CH with the help of fuzzy inference system in a distributed way. The experimental results indicate EEDCF algorithm is better than some current representative methods in aspects of data transmission, energy consumption and lifetime of networks. PMID:28671641

  11. Distribution and dynamics of hayscented fern following stand harvest

    Science.gov (United States)

    Songlin Fei; Peter J. Gould; Melanie J. Kaeser; Kim C. Steiner

    2008-01-01

    The distribution and dynamics of hayscented fern were examined as part of a large-scale study of oak regeneration in Pennsylvania. The study included 69 stands covering 3,333 acres in two physiographic provinces. Hayscented fern was more widely distributed and occurred at higher densities in the Allegheny Plateau physiographic provinces versus the Ridge and Valley...

  12. Electric Vehicle (EV) Charging Management with Dynamic Distribution System Tariff

    DEFF Research Database (Denmark)

    O'Connell, Niamh; Wu, Qiuwei; Østergaard, Jacob

    2011-01-01

    An electric vehicle (EV) charging schedule algorithm was proposed in this paper in order to charge EVs to meet EV users’ driving needs with the minimum EV charging cost and respect the local distribution system constraints. A day-ahead dynamic distribution system tariff scheme was proposed to avoid...

  13. Approximate Solutions of Interactive Dynamic Influence Diagrams Using Model Clustering

    DEFF Research Database (Denmark)

    Zeng, Yifeng; Doshi, Prashant; Qiongyu, Cheng

    2007-01-01

    Interactive dynamic influence diagrams (I-DIDs) offer a transparent and semantically clear representation for the sequential decision-making problem over multiple time steps in the presence of other interacting agents. Solving I-DIDs exactly involves knowing the solutions of possible models...

  14. A comparative study of spatially clustered distribution of jumbo flying squid ( Dosidicus gigas) offshore Peru

    Science.gov (United States)

    Feng, Yongjiu; Cui, Li; Chen, Xinjun; Liu, Yu

    2017-06-01

    We examined spatially clustered distribution of jumbo flying squid ( Dosidicus gigas) in the offshore waters of Peru bounded by 78°-86°W and 8°-20°S under 0.5°×0.5° fishing grid. The study is based on the catch-per-unit-effort (CPUE) and fishing effort from Chinese mainland squid jigging fleet in 2003-2004 and 2006-2013. The data for all years as well as the eight years (excluding El Niño events) were studied to examine the effect of climate variation on the spatial distribution of D. gigas. Five spatial clusters reflecting the spatial distribution were computed using K-means and Getis-Ord Gi* for a detailed comparative study. Our results showed that clusters identified by the two methods were quite different in terms of their spatial patterns, and K-means was not as accurate as Getis-Ord Gi*, as inferred from the agreement degree and receiver operating characteristic. There were more areas of hot and cold spots in years without the impact of El Niño, suggesting that such large-scale climate variations could reduce the clustering level of D. gigas. The catches also showed that warm El Niño conditions and high water temperature were less favorable for D. gigas offshore Peru. The results suggested that the use of K-means is preferable if the aim is to discover the spatial distribution of each sub-region (cluster) of the study area, while Getis-Ord Gi* is preferable if the aim is to identify statistically significant hot spots that may indicate the central fishing ground.

  15. Multidimensional Dynamic Programming Algorithm for N-Level Batching with Hierarchical Clustering Structure

    Directory of Open Access Journals (Sweden)

    Seung-Kil Lim

    2017-01-01

    Full Text Available This study focuses on the N-level batching problem with a hierarchical clustering structure. Clustering is the task of grouping a set of item types in such a way that item types in the same cluster are more similar (in some sense or another to each other than to those in other clusters. In hierarchical clustering structure, more and more different item types are clustered together as the level of the hierarchy increases. N-level batching is the process by which items with different types are grouped into several batches passed from level 1 to level N sequentially for given hierarchical clustering structure such that batches in each level should satisfy the maximum and minimum batch size requirements of the level. We consider two types of processing costs of the batches: unit processing cost and batch processing cost. We formulate the N-level batching problem with a hierarchical clustering structure as a nonlinear integer programming model with the objective of minimizing the total processing cost. To solve the problem optimally, we propose a multidimensional dynamic programming algorithm with an example.

  16. Antisymmetrized molecular dynamics studies for exotic clustering phenomena in neutron-rich nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Kimura, M. [Hokkaido University, Department of Physics, Sapporo (Japan); Hokkaido University, Nuclear Reaction Data Centre, Faculty of Science, Sapporo (Japan); Suhara, T. [Matsue College of Technology, Matsue (Japan); Kanada-En' yo, Y. [Kyoto University, Department of Physics, Kyoto (Japan)

    2016-12-15

    We present a review of recent works on clustering phenomena in unstable nuclei studied by antisymmetrized molecular dynamics (AMD). The AMD studies in these decades have uncovered novel types of clustering phenomena brought about by the excess neutrons. Among them, this review focuses on the molecule-like structure of unstable nuclei. One of the earliest discussions on the clustering in unstable nuclei was made for neutron-rich Be and B isotopes. AMD calculations predicted that the ground state clustering is enhanced or reduced depending on the number of excess neutrons. Today, the experiments are confirming this prediction as the change of the proton radii. Behind this enhancement and reduction of the clustering, there are underlying shell effects called molecular and atomic orbits. These orbits form covalent and ionic bonding of the clusters analogous to the atomic molecules. It was found that this ''molecular-orbit picture'' reasonably explains the low-lying spectra of Be isotopes. The molecular-orbit picture is extended to other systems having parity asymmetric cluster cores and to the three cluster systems. O and Ne isotopes are the candidates of the former, while the 3α linear chains in C isotopes are the latter. For both subjects, many intensive studies are now in progress. We also pay a special attention to the observables which are the fingerprint of the clustering. In particular, we focus on the monopole and dipole transitions which are recently regarded as good probe for the clustering. We discuss how they have and will reveal the exotic clustering. (orig.)

  17. Centroid path integral molecular dynamics simulation of lithium para-hydrogen clusters

    Science.gov (United States)

    Kinugawa, Kenichi; Moore, Preston B.; Klein, Michael L.

    1997-01-01

    The real-time quantum dynamics of a series of lithium para-hydrogen clusters, Li(p-H2)n (n=13, 55, and 180), has been investigated at 2.5 and 4.0 K by means of normal mode centroid path integral molecular dynamics (NMCMD) simulation, following the methodology originally proposed by Cao and Voth [J. Chem. Phys. 101, 6168 (1994)]. The Li(p-H2)34 and neat (p-H2)34 clusters have also been simulated at 2.5 K to see the effect of doping of a Li atom on the cluster dynamics. We explicitly display both the microcanonical and the constant-temperature equations of motion for NMCMD simulations using the Nosé-Hoover chain thermostats and the reference system propagator algorithm (RESPA). In addition to the energetic and structural properties, the real-time semi-classical dynamics of the centroids of the Li atom and p-H2 molecules in the clusters has been explored to investigate the diffusive and vibrational properties. In general, quantization of the nuclear motion enhances the ease of melting and diffusion, and also causes the power spectra of the velocity autocorrelation functions of hydrogen molecules to be dramatically shifted to lower frequency than in the classical regime. The self-diffusion coefficient of p-H2 molecules in the Li(p-H2)13 cluster, which is melted completely at both 2.5 and 4.0 K, is comparable to the experimental value of bulk liquid p-H2 just above the melting temperature (14 K). No significant differences have been found for the structural properties, molecular diffusion, and the quantum vibrational spectra of p-H2 molecules between the neat (p-H2)34 and Li(p-H2)34 clusters at 2.5 K. The n=34, 55, and 180 clusters show a solidlike core and a tendency towards surface melting at 2.5 K, with diffusion restricted to the outer region. The core of the Li(p-H2)55 cluster exhibits slow liquidlike diffusion at 4.0 K, whereas that of the Li(p-H2)180 cluster remains solidlike at this temperature. The quantum power spectrum of the velocity autocorrelation

  18. Combining in situ transmission electron microscopy irradiation experiments with cluster dynamics modeling to study nanoscale defect agglomeration in structural metals

    International Nuclear Information System (INIS)

    Xu Donghua; Wirth, Brian D.; Li Meimei; Kirk, Marquis A.

    2012-01-01

    We present a combinatorial approach that integrates state-of-the-art transmission electron microscopy (TEM) in situ irradiation experiments and high-performance computing techniques to study irradiation defect dynamics in metals. Here, we have studied the evolution of visible defect clusters in nanometer-thick molybdenum foils under 1 MeV krypton ion irradiation at 80 °C through both cluster dynamics modeling and in situ TEM experiments. The experimental details are reported elsewhere; we focus here on the details of model construction and comparing the model with the experiments. The model incorporates continuous production of point defects and/or small clusters, and the accompanying interactions, which include clustering, recombination and loss to the surfaces that result from the diffusion of the mobile defects. To account for the strong surface effect in thin TEM foils, the model includes one-dimensional spatial dependence along the foil depth, and explicitly treats the surfaces as black sinks. The rich amount of data (cluster number density and size distribution at a variety of foil thickness, irradiation dose and dose rate) offered by the advanced in situ experiments has allowed close comparisons with computer modeling and permitted significant validation and optimization of the model in terms of both physical model construct (damage production mode, identities of mobile defects) and parameterization (diffusivities of mobile defects). The optimized model exhibits good qualitative and quantitative agreement with the in situ TEM experiments. The combinatorial approach is expected to bring a unique opportunity for the study of radiation damage in structural materials.

  19. A Fractal Approach to Dynamic Inference and Distribution Analysis

    Directory of Open Access Journals (Sweden)

    Marieke M.J.W. van Rooij

    2013-01-01

    Full Text Available Event-distributions inform scientists about the variability and dispersion of repeated measurements. This dispersion can be understood from a complex systems perspective, and quantified in terms of fractal geometry. The key premise is that a distribution’s shape reveals information about the governing dynamics of the system that gave rise to the distribution. Two categories of characteristic dynamics are distinguished: additive systems governed by component-dominant dynamics and multiplicative or interdependent systems governed by interaction-dominant dynamics. A logic by which systems governed by interaction-dominant dynamics are expected to yield mixtures of lognormal and inverse power-law samples is discussed. These mixtures are described by a so-called cocktail model of response times derived from human cognitive performances. The overarching goals of this article are twofold: First, to offer readers an introduction to this theoretical perspective and second, to offer an overview of the related statistical methods.

  20. Spatial distribution and temporal evolution of DRONPA-fused SNAP25 clusters in adrenal chromaffin cells

    DEFF Research Database (Denmark)

    Antoku, Yasuko; Dedecker, Peter; da Silva Pinheiro, Paulo César

    2015-01-01

    fluorescence bursts of DRONPA-fused SNAP-25 molecules in live chromaffin cells by Total Internal Reflection Fluorescence (TIRF) imaging. We find that this method allows tracking protein cluster dynamics over relatively long times (∼20 min.), partly due to the diffusion into the TIRF field of fresh molecules......Sub-diffraction imaging of plasma membrane localized proteins, such as the SNARE (Soluble NSF Attachment Protein Receptor) proteins involved in exocytosis, in fixed cells have resulted in images with high spatial resolution, at the expense of dynamical information. Here, we have imaged localized...

  1. Electron localization in water clusters

    International Nuclear Information System (INIS)

    Landman, U.; Barnett, R.N.; Cleveland, C.L.; Jortner, J.

    1987-01-01

    Electron attachment to water clusters was explored by the quantum path integral molecular dynamics method, demonstrating that the energetically favored localization mode involves a surface state of the excess electron, rather than the precursor of the hydrated electron. The cluster size dependence, the energetics and the charge distribution of these novel electron-cluster surface states are explored. 20 refs., 2 figs., 1 tab

  2. YOUNG STELLAR CLUSTERS WITH A SCHUSTER MASS DISTRIBUTION. I. STATIONARY WINDS

    Energy Technology Data Exchange (ETDEWEB)

    Palous, Jan; Wuensch, Richard; Hueyotl-Zahuantitla, Filiberto [Astronomical Institute, Academy of Sciences of the Czech Republic, Bocni II 1401-2a, Prague (Czech Republic); Martinez-Gonzalez, Sergio; Silich, Sergiy; Tenorio-Tagle, Guillermo, E-mail: palous@ig.cas.cz [Instituto Nacional de Astrofisica Optica y Electronica, AP 51, 72000 Puebla (Mexico)

    2013-08-01

    Hydrodynamic models for spherically symmetric winds driven by young stellar clusters with a generalized Schuster stellar density profile are explored. For this we use both semi-analytic models and one-dimensional numerical simulations. We determine the properties of quasi-adiabatic and radiative stationary winds and define the radius at which the flow turns from subsonic to supersonic for all stellar density distributions. Strongly radiative winds significantly diminish their terminal speed and thus their mechanical luminosity is strongly reduced. This also reduces their potential negative feedback into their host galaxy interstellar medium. The critical luminosity above which radiative cooling becomes dominant within the clusters, leading to thermal instabilities which make the winds non-stationary, is determined, and its dependence on the star cluster density profile, core radius, and half-mass radius is discussed.

  3. Topological clustering as a tool for planning water quality monitoring in water distribution networks

    DEFF Research Database (Denmark)

    Kirstein, Jonas Kjeld; Albrechtsen, Hans-Jørgen; Rygaard, Martin

    2015-01-01

    identification of potential contamination and affected consumers in contamination cases. Although still in development, the method shows potential for assisting utilities during planning of monitoring programs and as decision support tool during emergency contingency situations.......Topological clustering was explored as a tool for water supply utilities in preparation of monitoring and contamination contingency plans. A complex water distribution network model of Copenhagen, Denmark, was simplified by topological clustering into recognizable water movement patterns to: (1......) identify steady clusters for a part of the network where an actual contamination has occurred; (2) analyze this event by the use of mesh diagrams; and (3) analyze the use of mesh diagrams as a decision support tool for planning water quality monitoring. Initially, the network model was divided...

  4. Investigating the Relation between Galaxy Properties and the Gaussianity of the Velocity Distribution of Groups and Clusters

    Science.gov (United States)

    de Carvalho, R. R.; Ribeiro, A. L. B.; Stalder, D. H.; Rosa, R. R.; Costa, A. P.; Moura, T. C.

    2017-09-01

    We investigate the dependence of stellar population properties of galaxies on group dynamical stage for a subsample of the Yang catalog. We classify groups according to their galaxy velocity distribution into Gaussian (G) and Non-Gaussian (NG). Using two totally independent approaches, we have shown that our measurement of Gaussianity is robust and reliable. Our sample covers Yang’s groups in the redshift range 0.03 ≤slant z ≤slant 0.1, with mass ≥slant {10}14{M}⊙ . The new method, called Hellinger Distance, to determine whether a group has a velocity distribution Gaussian or NG is very effective in distinguishing between the two families. NG groups present halo masses higher than the G ones, confirming previous findings. Examining the skewness and kurtosis of the velocity distribution of G and NG groups, we find that faint galaxies in NG groups are mainly infalling, for the first time, into the groups. We show that considering only faint galaxies in the outskirts; those in NG groups are older and more metal-rich than those in G groups. Also, examining the Projected Phase Space of cluster galaxies, we see that bright and faint galactic systems in G groups are in dynamical equilibrium—which does not seem to be the case in NG groups. These findings suggest that NG systems have a higher infall rate, assembling more galaxies that have experienced preprocessing before entering the group.

  5. Distribution of cardiac sodium channels in clusters potentiates ephaptic interactions in the intercalated disc.

    Science.gov (United States)

    Hichri, Echrak; Abriel, Hugues; Kucera, Jan P

    2018-02-15

    It has been proposed that ephaptic conduction, relying on interactions between the sodium (Na + ) current and the extracellular potential in intercalated discs, might contribute to cardiac conduction when gap junctional coupling is reduced, but this mechanism is still controversial. In intercalated discs, Na + channels form clusters near gap junction plaques, but the functional significance of these clusters has never been evaluated. In HEK cells expressing cardiac Na + channels, we show that restricting the extracellular space modulates the Na + current, as predicted by corresponding simulations accounting for ephaptic effects. In a high-resolution model of the intercalated disc, clusters of Na + channels that face each other across the intercellular cleft facilitate ephaptic impulse transmission when gap junctional coupling is reduced. Thus, our simulations reveal a functional role for the clustering of Na + channels in intercalated discs, and suggest that rearrangement of these clusters in disease may influence cardiac conduction. It has been proposed that ephaptic interactions in intercalated discs, mediated by extracellular potentials, contribute to cardiac impulse propagation when gap junctional coupling is reduced. However, experiments demonstrating ephaptic effects on the cardiac Na + current (I Na ) are scarce. Furthermore, Na + channels form clusters around gap junction plaques, but the electrophysiological significance of these clusters has never been investigated. In patch clamp experiments with HEK cells stably expressing human Na v 1.5 channels, we examined how restricting the extracellular space modulates I Na elicited by an activation protocol. In parallel, we developed a high-resolution computer model of the intercalated disc to investigate how the distribution of Na + channels influences ephaptic interactions. Approaching the HEK cells to a non-conducting obstacle always increased peak I Na at step potentials near the threshold of I Na activation

  6. Priority Based Congestion Control Dynamic Clustering Protocol in Mobile Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    R. Beulah Jayakumari

    2015-01-01

    Full Text Available Wireless sensor network is widely used to monitor natural phenomena because natural disaster has globally increased which causes significant loss of life, economic setback, and social development. Saving energy in a wireless sensor network (WSN is a critical factor to be considered. The sensor nodes are deployed to sense, compute, and communicate alerts in a WSN which are used to prevent natural hazards. Generally communication consumes more energy than sensing and computing; hence cluster based protocol is preferred. Even with clustering, multiclass traffic creates congested hotspots in the cluster, thereby causing packet loss and delay. In order to conserve energy and to avoid congestion during multiclass traffic a novel Priority Based Congestion Control Dynamic Clustering (PCCDC protocol is developed. PCCDC is designed with mobile nodes which are organized dynamically into clusters to provide complete coverage and connectivity. PCCDC computes congestion at intra- and intercluster level using linear and binary feedback method. Each mobile node within the cluster has an appropriate queue model for scheduling prioritized packet during congestion without drop or delay. Simulation results have proven that packet drop, control overhead, and end-to-end delay are much lower in PCCDC which in turn significantly increases packet delivery ratio, network lifetime, and residual energy when compared with PASCC protocol.

  7. Fast optimization of binary clusters using a novel dynamic lattice searching method

    International Nuclear Information System (INIS)

    Wu, Xia; Cheng, Wen

    2014-01-01

    Global optimization of binary clusters has been a difficult task despite of much effort and many efficient methods. Directing toward two types of elements (i.e., homotop problem) in binary clusters, two classes of virtual dynamic lattices are constructed and a modified dynamic lattice searching (DLS) method, i.e., binary DLS (BDLS) method, is developed. However, it was found that the BDLS can only be utilized for the optimization of binary clusters with small sizes because homotop problem is hard to be solved without atomic exchange operation. Therefore, the iterated local search (ILS) method is adopted to solve homotop problem and an efficient method based on the BDLS method and ILS, named as BDLS-ILS, is presented for global optimization of binary clusters. In order to assess the efficiency of the proposed method, binary Lennard-Jones clusters with up to 100 atoms are investigated. Results show that the method is proved to be efficient. Furthermore, the BDLS-ILS method is also adopted to study the geometrical structures of (AuPd) 79 clusters with DFT-fit parameters of Gupta potential

  8. Dynamics of the baryonic component in hierarchical clustering universes

    Science.gov (United States)

    Navarro, Julio

    1993-01-01

    I present self-consistent 3-D simulations of the formation of virialized systems containing both gas and dark matter in a flat universe. A fully Lagrangian code based on the Smoothed Particle Hydrodynamics technique and a tree data structure has been used to evolve regions of comoving radius 2-3 Mpc. Tidal effects are included by coarse-sampling the density of the outer regions up to a radius approx. 20 Mpc. Initial conditions are set at high redshift (z greater than 7) using a standard Cold Dark Matter perturbation spectrum and a baryon mass fraction of 10 percent (omega(sub b) = 0.1). Simulations in which the gas evolves either adiabatically or radiates energy at a rate determined locally by its cooling function were performed. This allows us to investigate with the same set of simulations the importance of radiative losses in the formation of galaxies and the equilibrium structure of virialized systems where cooling is very inefficient. In the absence of radiative losses, the simulations can be rescaled to the density and radius typical of galaxy clusters. A summary of the main results is presented.

  9. Nonlinear dynamics of clustering in particle-laden turbulent flows

    Science.gov (United States)

    Esmaily, Mahdi; Mani, Ali

    2017-11-01

    Heavy inertial particles in spatially and temporally varying flows can form clusters if their relaxation time is on the order of the dissipation time scale of the flow. This regime, identified by St = O (1) , is investigated in this study using analytical tools. We show that the nonlinear variation of segregation versus St can be explained by considering a one-dimensional canonical setting where particles are subjected to an oscillatory velocity gradient that is constant in space. Our analysis shows that the Lyapunov exponent, as a measure of particle segregation, reaches a minimum at St = O (1) and becomes positive at St >> 1 and approaches zero as St -> 0 or ∞. These predictions, which are corroborated by the numerical results, are directly linked and compared against measurements of the dispersion and segregation in three-dimensional turbulence. Our analysis reveals a strongly nonlinear behavior of the Lyapunov exponents in the straining regimes of strong oscillations. This work was supported by the United States Department of Energy under the Predictive Science Academic Alliance Program 2 (PSAAP2) at Stanford University.

  10. Dynamics of atomic clusters in intense optical fields of ultrashort ...

    Indian Academy of Sciences (India)

    be considered archetypal. Note that (i) maximum ener- gies approaching 1 MeV are obtained for Ar40,000, and. (ii) the shape of the energy distribution has a knee- like structure, in the region of 100 keV in the case depicted in figure 1, that delineates two regions of diffe- rent slopes. This shape has been found to be typical ...

  11. Dynamic radial distribution function from inelastic neutron scattering

    International Nuclear Information System (INIS)

    McQueeney, R.J.

    1998-01-01

    A real-space, local dynamic structure function g(r,ω) is defined from the dynamic structure function S(Q,ω), which can be measured using inelastic neutron scattering. At any particular frequency ω, S(Q,ω) contains Q-dependent intensity oscillations which reflect the spatial distribution and relative displacement directions for the atoms vibrating at that frequency. Information about local and dynamic atomic correlations is obtained from the Fourier transform of these oscillations g(r,ω) at the particular frequency. g(r,ω) can be formulated such that the elastic and frequency-summed limits correspond to the average and instantaneous radial distribution function, respectively, and is thus called the dynamic radial distribution function. As an example, the dynamic radial distribution function is calculated for fcc nickel in a model which considers only the harmonic atomic displacements due to phonons. The results of these calculations demonstrate that the magnitude of the atomic correlations can be quantified and g(r,ω) is a well-defined correlation function. This leads to a simple prescription for investigating local lattice dynamics. copyright 1998 The American Physical Society

  12. An improved energy aware distributed unequal clustering protocol for heterogeneous wireless sensor networks

    Directory of Open Access Journals (Sweden)

    Vrinda Gupta

    2016-06-01

    Full Text Available In this paper, an improved version of the energy aware distributed unequal clustering protocol (EADUC is projected. The EADUC protocol is commonly used for solving energy hole problem in multi-hop wireless sensor networks. In the EADUC, location of base station and residual energy are given importance as clustering parameters. Based on these parameters, different competition radii are assigned to nodes. Herein, a new approach has been proposed to improve the working of EADUC, by electing cluster heads considering number of nodes in the neighborhood in addition to the above two parameters. The inclusion of the neighborhood information for computation of the competition radii provides better balancing of energy in comparison with the existing approach. Furthermore, for the selection of next hop node, the relay metric is defined directly in terms of energy expense instead of only the distance information used in the EADUC and the data transmission phase has been extended in every round by performing the data collection number of times through use of major slots and mini-slots. The methodology used is of retaining the same clusters for a few rounds and is effective in reducing the clustering overhead. The performance of the proposed protocol has been evaluated under three different scenarios and compared with existing protocols through simulations. The results show that the proposed scheme outperforms the existing protocols in terms of network lifetime in all the scenarios.

  13. Molecular diagnostics based on clustering dynamics of magnetic nanobeads

    DEFF Research Database (Denmark)

    Donolato, Marco; Bejhed, Rebecca S.; de la Torre, Teresa Zardán Gómez

    2014-01-01

    or on the polymerase chain reaction (PCR) [1]. In this work we demonstrate detection of DNA coils formed from a Vibrio Cholerae DNA target at pM concentrations using a novel opto-magnetic approach exploiting the dynamic collective behavior of magnetic nanobeads. The technique relies on measurements of the light...... and isothermal rolling circle amplification from Vibrio cholerae DNA. The detection method is shown in Figure 1. MNBs which specifically bind to the micrometric sized DNA coil cannot rotate under the field action as free beads and form chains; this results in a strongly modified opto-magnetic signal. As a core...

  14. Proton transfer reactions and dynamics in protonated water clusters.

    Science.gov (United States)

    Lao-Ngam, Charoensak; Asawakun, Prapasri; Wannarat, Sornthep; Sagarik, Kritsana

    2011-03-14

    Proton transfer reactions and dynamics were theoretically studied using the hydrogen-bond (H-bond) complexes formed from H(3)O(+) and nH(2)O, n = 1-4, as model systems. The investigations began with searching for characteristics of transferring protons in the gas phase and continuum aqueous solution using DFT method at the B3LYP/TZVP level, followed by Born-Oppenheimer molecular dynamics (BOMD) simulations at 350 K. B3LYP/TZVP calculations revealed the threshold asymmetric O-H stretching frequencies (ν(OH)*) for the proton transfers in the Zundel complex (H(5)O) in the gas phase and continuum aqueous solution at 1984 and 1881 cm(-1), respectively. BOMD simulations suggested lower threshold frequencies (ν(OH,MD)* = 1917 and 1736 cm(-1), respectively), with two characteristic ν(OH,MD) being the IR spectral signatures of the transferring protons. The low-frequency band could be associated with the "oscillatory shuttling motion" and the high-frequency band with the "structural diffusion motion". These can be regarded as the spectroscopic evidences of the formations of the shared-proton structure (O···H(+)···O) and the H(3)O(+)-H(2)O contact structure (O-H(+)···O), respectively. Since the quasi-dynamic equilibrium between the Zundel and Eigen complexes was suggested to be the rate-determining step, in order to achieve an "ideal" maximum efficiency of proton transfer, a concerted reaction pathway should be taken. The most effective interconversion between the two proton states, the shared-proton structure and the H(3)O(+)-H(2)O contact structure, can be reflected from comparable intensities of the oscillatory shuttling and structural diffusion bands. The present results iterated the previous conclusions that static proton transfer potentials cannot provide complete description of the structural diffusion process and it is essential to incorporate thermal energy fluctuations and dynamics in the model calculations.

  15. Contributed Review: Distributed optical fibre dynamic strain sensing.

    Science.gov (United States)

    Masoudi, Ali; Newson, Trevor P

    2016-01-01

    Extensive research on Brillouin- and Raman-based distributed optical fibre sensors over the past two decades has resulted in the commercialization of distributed sensors capable of measuring static and quasi-static phenomena such as temperature and strain. Recently, the focus has been shifted towards developing distributed sensors for measurement of dynamic phenomena such as dynamic strain and sound waves. This article reviews the current state of the art distributed optical fibre sensors capable of quantifying dynamic vibrations. The most important aspect of Rayleigh and Brillouin scattering processes which have been used for distributed dynamic measurement are studied. The principle of the sensing techniques used to measure dynamic perturbations are analyzed followed by a case study of the most recent advances in this field. It is shown that the Rayleigh-based sensors have longer sensing range and higher frequency range, but their spatial resolution is limited to 1 m. On the other hand, the Brillouin-based sensors have shown a higher spatial resolution, but relatively lower frequency and sensing ranges.

  16. Dynamical equivalence, the origin of the Galactic field stellar and binary population, and the initial radius-mass relation of embedded clusters

    Science.gov (United States)

    Belloni, Diogo; Kroupa, Pavel; Rocha-Pinto, Helio J.; Giersz, Mirek

    2018-03-01

    In order to allow a better understanding of the origin of Galactic field populations, dynamical equivalence of stellar-dynamical systems has been postulated by Kroupa and Belloni et al. to allow mapping of solutions of the initial conditions of embedded clusters such that they yield, after a period of dynamical processing, the Galactic field population. Dynamically equivalent systems are defined to initially and finally have the same distribution functions of periods, mass ratios and eccentricities of binary stars. Here, we search for dynamically equivalent clusters using the MOCCA code. The simulations confirm that dynamically equivalent solutions indeed exist. The result is that the solution space is next to identical to the radius-mass relation of Marks & Kroupa, ( r_h/pc )= 0.1^{+0.07}_{-0.04} ( M_ecl/M_{⊙} )^{0.13± 0.04}. This relation is in good agreement with the oIMF. This is achieved by applying a similar procedurebserved density of molecular cloud clumps. According to the solutions, the time-scale to reach dynamical equivalence is about 0.5 Myr which is, interestingly, consistent with the lifetime of ultra-compact H II regions and the time-scale needed for gas expulsion to be active in observed very young clusters as based on their dynamical modelling.

  17. cluster

    Indian Academy of Sciences (India)

    has been investigated electrochemically in positive and negative microenvironments, both in solution and in film. Charge nature around the active centre ... in plants, bacteria and also in mammals. This cluster is also an important constituent of a ..... selection of non-cysteine amino acid in the active centre of Rieske proteins.

  18. Water droplet excess free energy determined by cluster mitosis using guided molecular dynamics

    Science.gov (United States)

    Lau, Gabriel V.; Hunt, Patricia A.; Müller, Erich A.; Jackson, George; Ford, Ian J.

    2015-12-01

    Atmospheric aerosols play a vital role in affecting climate by influencing the properties and lifetimes of clouds and precipitation. Understanding the underlying microscopic mechanisms involved in the nucleation of aerosol droplets from the vapour phase is therefore of great interest. One key thermodynamic quantity in nucleation is the excess free energy of cluster formation relative to that of the saturated vapour. In our current study, the excess free energy is extracted for clusters of pure water modelled with the TIP4P/2005 intermolecular potential using a method based on nonequilibrium molecular dynamics and the Jarzynski relation. The change in free energy associated with the "mitosis" or division of a cluster of N water molecules into two N/2 sub-clusters is evaluated. This methodology is an extension of the disassembly procedure used recently to calculate the excess free energy of argon clusters [H. Y. Tang and I. J. Ford, Phys. Rev. E 91, 023308 (2015)]. Our findings are compared to the corresponding excess free energies obtained from classical nucleation theory (CNT) as well as internally consistent classical theory (ICCT). The values of the excess free energy that we obtain with the mitosis method are consistent with CNT for large cluster sizes but for the smallest clusters, the results tend towards ICCT; for intermediate sized clusters, we obtain values between the ICCT and CNT predictions. Furthermore, the curvature-dependent surface tension which can be obtained by regarding the clusters as spherical droplets of bulk density is found to be a monotonically increasing function of cluster size for the studied range. The data are compared to other values reported in the literature, agreeing qualitatively with some but disagreeing with the values determined by Joswiak et al. [J. Phys. Chem. Lett. 4, 4267 (2013)] using a biased mitosis approach; an assessment of the differences is the main motivation for our current study.

  19. Water droplet excess free energy determined by cluster mitosis using guided molecular dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Lau, Gabriel V.; Müller, Erich A.; Jackson, George [Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom); Hunt, Patricia A. [Department of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom); Ford, Ian J. [Department of Physics and Astronomy and London Centre for Nanotechnology, University College London, Gower Street, London WC1E 6BT (United Kingdom)

    2015-12-28

    Atmospheric aerosols play a vital role in affecting climate by influencing the properties and lifetimes of clouds and precipitation. Understanding the underlying microscopic mechanisms involved in the nucleation of aerosol droplets from the vapour phase is therefore of great interest. One key thermodynamic quantity in nucleation is the excess free energy of cluster formation relative to that of the saturated vapour. In our current study, the excess free energy is extracted for clusters of pure water modelled with the TIP4P/2005 intermolecular potential using a method based on nonequilibrium molecular dynamics and the Jarzynski relation. The change in free energy associated with the “mitosis” or division of a cluster of N water molecules into two N/2 sub-clusters is evaluated. This methodology is an extension of the disassembly procedure used recently to calculate the excess free energy of argon clusters [H. Y. Tang and I. J. Ford, Phys. Rev. E 91, 023308 (2015)]. Our findings are compared to the corresponding excess free energies obtained from classical nucleation theory (CNT) as well as internally consistent classical theory (ICCT). The values of the excess free energy that we obtain with the mitosis method are consistent with CNT for large cluster sizes but for the smallest clusters, the results tend towards ICCT; for intermediate sized clusters, we obtain values between the ICCT and CNT predictions. Furthermore, the curvature-dependent surface tension which can be obtained by regarding the clusters as spherical droplets of bulk density is found to be a monotonically increasing function of cluster size for the studied range. The data are compared to other values reported in the literature, agreeing qualitatively with some but disagreeing with the values determined by Joswiak et al. [J. Phys. Chem. Lett. 4, 4267 (2013)] using a biased mitosis approach; an assessment of the differences is the main motivation for our current study.

  20. Dynamics and molecular determinants of cytoplasmic lipid droplet clustering and dispersion.

    Directory of Open Access Journals (Sweden)

    David J Orlicky

    Full Text Available Perilipin-1 (Plin1, a prominent cytoplasmic lipid droplet (CLD binding phosphoprotein and key physiological regulator of triglyceride storage and lipolysis in adipocytes, is thought to regulate the fragmentation and dispersion of CLD that occurs in response to β-adrenergic activation of adenylate cyclase. Here we investigate the dynamics and molecular determinants of these processes using cell lines stably expressing recombinant forms of Plin1 and/or other members of the perilipin family. Plin1 and a C-terminal CLD-binding fragment of Plin1 (Plin1CT induced formation of single dense CLD clusters near the microtubule organizing center, whereas neither an N-terminal CLD-binding fragment of Plin1, nor Plin2 or Plin3 induced clustering. Clustered CLD coated by Plin1, or Plin1CT, dispersed in response to isoproterenol, or other agents that activate adenylate cyclase, in a process inhibited by the protein kinase A inhibitor, H89, and blocked by microtubule disruption. Isoproterenol-stimulated phosphorylation of CLD-associated Plin1 on serine 492 preceded their dispersion, and live cell imaging showed that cluster dispersion involved initial fragmentation of tight clusters into multiple smaller clusters, which then fragmented into well-dispersed individual CLD. siRNA knockdown of the cortical actin binding protein, moesin, induced disaggregation of tight clusters into multiple smaller clusters, and inhibited the reaggregation of dispersed CLD into tight clusters. Together these data suggest that the clustering and dispersion processes involve a complex orchestration of phosphorylation-dependent, microtubule-dependent and independent, and microfilament dependent steps.

  1. Cluster galaxy population evolution from the Subaru Hyper Suprime-Cam survey: brightest cluster galaxies, stellar mass distribution, and active galaxies

    Science.gov (United States)

    Lin, Yen-Ting; Hsieh, Bau-Ching; Lin, Sheng-Chieh; Oguri, Masamune; Chen, Kai-Feng; Tanaka, Masayuki; Chiu, I.-non; Huang, Song; Kodama, Tadayuki; Leauthaud, Alexie; More, Surhud; Nishizawa, Atsushi J.; Bundy, Kevin; Lin, Lihwai; Miyazaki, Satoshi; HSC Collaboration

    2018-01-01

    The unprecedented depth and area surveyed by the Subaru Strategic Program with the Hyper Suprime-Cam (HSC-SSP) have enabled us to construct and publish the largest distant cluster sample out to z~1 to date. In this exploratory study of cluster galaxy evolution from z=1 to z=0.3, we investigate the stellar mass assembly history of brightest cluster galaxies (BCGs), and evolution of stellar mass and luminosity distributions, stellar mass surface density profile, as well as the population of radio galaxies. Our analysis is the first high redshift application of the top N richest cluster selection, which is shown to allow us to trace the cluster galaxy evolution faithfully. Our stellar mass is derived from a machine-learning algorithm, which we show to be unbiased and accurate with respect to the COSMOS data. We find very mild stellar mass growth in BCGs, and no evidence for evolution in both the total stellar mass-cluster mass correlation and the shape of the stellar mass surface density profile. The clusters are found to contain more red galaxies compared to the expectations from the field, even after the differences in density between the two environments have been taken into account. We also present the first measurement of the radio luminosity distribution in clusters out to z~1.

  2. Monitoring And Analyzing Distributed Cluster Performance And Statistics Of Atlas Job Flow

    CERN Document Server

    Ramprakash, S

    2005-01-01

    The ATLAS experiment is a High Energy Physics experiment that utilizes the services of Grid3 now migrating to the Open Science Grid (OSG). This thesis provides monitoring and analysis of performance and statistical data from individual distributed clusters that combine to form the ATLAS Grid and will ultimately be used to make scheduling decisions on this Grid. The system developed in this thesis uses a layered architecture such that predicted future developments or changes brought to the existing Grid infrastructure can easily utilize this work with minimum or no changes. The starting point of the system is based on the existing scheduling that is being done manually for ATLAS job flow. We have provided additional functionality based on the requirements of the High Energy Physics ATLAS team of physicists at UTA. The system developed in this thesis has successfully monitored and analyzed distributed cluster performance at three sites and is waiting for access to monitor data from three more sites. (Abstract s...

  3. Learning Based Approach for Optimal Clustering of Distributed Program's Call Flow Graph

    Science.gov (United States)

    Abofathi, Yousef; Zarei, Bager; Parsa, Saeed

    Optimal clustering of call flow graph for reaching maximum concurrency in execution of distributable components is one of the NP-Complete problems. Learning automatas (LAs) are search tools which are used for solving many NP-Complete problems. In this paper a learning based algorithm is proposed to optimal clustering of call flow graph and appropriate distributing of programs in network level. The algorithm uses learning feature of LAs to search in state space. It has been shown that the speed of reaching to solution increases remarkably using LA in search process, and it also prevents algorithm from being trapped in local minimums. Experimental results show the superiority of proposed algorithm over others.

  4. Precipitation Cluster Distributions: Current Climate Storm Statistics and Projected Changes Under Global Warming

    Science.gov (United States)

    Quinn, Kevin Martin

    The total amount of precipitation integrated across a precipitation cluster (contiguous precipitating grid cells exceeding a minimum rain rate) is a useful measure of the aggregate size of the disturbance, expressed as the rate of water mass lost or latent heat released, i.e. the power of the disturbance. Probability distributions of cluster power are examined during boreal summer (May-September) and winter (January-March) using satellite-retrieved rain rates from the Tropical Rainfall Measuring Mission (TRMM) 3B42 and Special Sensor Microwave Imager and Sounder (SSM/I and SSMIS) programs, model output from the High Resolution Atmospheric Model (HIRAM, roughly 0.25-0.5 0 resolution), seven 1-2° resolution members of the Coupled Model Intercomparison Project Phase 5 (CMIP5) experiment, and National Center for Atmospheric Research Large Ensemble (NCAR LENS). Spatial distributions of precipitation-weighted centroids are also investigated in observations (TRMM-3B42) and climate models during winter as a metric for changes in mid-latitude storm tracks. Observed probability distributions for both seasons are scale-free from the smallest clusters up to a cutoff scale at high cluster power, after which the probability density drops rapidly. When low rain rates are excluded by choosing a minimum rain rate threshold in defining clusters, the models accurately reproduce observed cluster power statistics and winter storm tracks. Changes in behavior in the tail of the distribution, above the cutoff, are important for impacts since these quantify the frequency of the most powerful storms. End-of-century cluster power distributions and storm track locations are investigated in these models under a "business as usual" global warming scenario. The probability of high cluster power events increases by end-of-century across all models, by up to an order of magnitude for the highest-power events for which statistics can be computed. For the three models in the suite with continuous

  5. Strong and weak lensing united: II. The cluster mass distribution of the most X-ray luminous cluster RX J1347.5-1145

    Energy Technology Data Exchange (ETDEWEB)

    Bradač, M.; Erben, T.; Schneider, P.; Hildebrandt, H.; Lombardi, M.; Schirmer, M.; Miralles, J. -M.; Clowe, D.; Schindler, S.

    2005-07-01

    We have shown that the cluster-mass reconstruction method which combines strong and weak gravitational lensing data, developed in the first paper in the series, successfully reconstructs the mass distribution of a simulated cluster. In this paper we apply the method to the ground-based high-quality multi-colour data of RX J1347.5-1145 , the most X-ray luminous cluster to date. A new analysis of the cluster core on very deep, multi-colour data analysis of VLT/FORS data reveals many more arc candidates than previously known for this cluster. The combined strong and weak lensing reconstruction confirms that the cluster is indeed very massive. If the redshift and identification of the multiple-image system as well as the redshift estimates of the source galaxies used for weak lensing are correct, we determine the enclosed cluster mass in a cylinder to M(<360 h -1 kpc)= (1.2± 0.3) x 1015 M. In addition the reconstructed mass distribution follows the distribution found with independent methods (X-ray measurements, SZ). With higher resolution (e.g. HST imaging data) more reliable multiple imaging information can be obtained and the reconstruction can be improved to accuracies greater than what is currently possible with weak and strong lensing techniques.

  6. Strong and Weak Lensing United II: the Cluster Mass Distribution of the Most X-ray Luminous Cluster RX J1347.5-1145

    Energy Technology Data Exchange (ETDEWEB)

    Bradac, M.

    2005-04-13

    We have shown that the cluster-mass reconstruction method which combines strong and weak gravitational lensing data, developed in the first paper in the series, successfully reconstructs the mass distribution of a simulated cluster. In this paper we apply the method to the ground-based high-quality multi-colour data of RX J1347.5-1145, the most X-ray luminous cluster to date. A new analysis of the cluster core on very deep, multi-colour data analysis of VLT/FORS data reveals many more arc candidates than previously known for this cluster. The combined strong and weak lensing reconstruction confirms that the cluster is indeed very massive. If the redshift and identification of the multiple-image system as well as the redshift estimates of the source galaxies used for weak lensing are correct, we determine the enclosed cluster mass in a cylinder to M(< 360h{sup -1}kpc) = (1.2 {+-} 0.3) x 10{sup 15}M{circle_dot}. In addition the reconstructed mass distribution follows the distribution found with independent methods (X-ray measurements, SZ). With higher resolution (e.g. HST imaging data) more reliable multiple imaging information can be obtained and the reconstruction can be improved to accuracies greater than what is currently possible with weak and strong lensing techniques.

  7. Dynamic stabilities of icosahedral-like clusters and their ability to form quasicrystals

    Directory of Open Access Journals (Sweden)

    Xiaogang Liang

    2016-06-01

    Full Text Available The dynamic stabilities of the icosahedral-like clusters containing up to 2200 atoms are investigated for 15 metal elements. The clusters originate from five different initial structures (icosahedron, truncated decahedron, octahedron, closed-shell fragment of an HCP structure, and non-closed-shell fragment of an HCP structure. The obtained order of the dynamic stabilities of the icosahedral-like clusters can be assigned to three groups, from stronger to weaker, according to the size ranges involved: (Zr, Al, Ti > (Cu, Fe, Co, Ni, Mg, Ag > (Pb, Au, Pd, Pt, Rh, Ir, which correspond to the predicted formation ability of the quasicrystals. Thedifferences of the sequences can be explained by analyzing the parameters of the Gupta-type many-body inter-atomic potentials.

  8. Dynamic stabilities of icosahedral-like clusters and their ability to form quasicrystals

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Xiaogang; Hamid, Ilyar; Duan, Haiming, E-mail: dhm@xju.edu.cn [College of Physics Science and Technology. Xinjiang University, Urumqi 830046 (China)

    2016-06-15

    The dynamic stabilities of the icosahedral-like clusters containing up to 2200 atoms are investigated for 15 metal elements. The clusters originate from five different initial structures (icosahedron, truncated decahedron, octahedron, closed-shell fragment of an HCP structure, and non-closed-shell fragment of an HCP structure). The obtained order of the dynamic stabilities of the icosahedral-like clusters can be assigned to three groups, from stronger to weaker, according to the size ranges involved: (Zr, Al, Ti) > (Cu, Fe, Co, Ni, Mg, Ag) > (Pb, Au, Pd, Pt, Rh, Ir), which correspond to the predicted formation ability of the quasicrystals. The differences of the sequences can be explained by analyzing the parameters of the Gupta-type many-body inter-atomic potentials.

  9. Experimental and theoretical investigation of the magnetization dynamics of an artificial square spin ice cluster

    Energy Technology Data Exchange (ETDEWEB)

    Pohlit, Merlin, E-mail: pohlit@physik.uni-frankfurt.de; Porrati, Fabrizio; Huth, Michael; Müller, Jens [Institute of Physics, Goethe-University Frankfurt, Frankfurt/Main (Germany); Stockem, Irina; Schröder, Christian [Bielefeld Institute for Applied Materials Research, FH Bielefeld-University of Applied Sciences, Bielefeld (Germany)

    2016-10-14

    We study the magnetization dynamics of a spin ice cluster which is a building block of an artificial square spin ice fabricated by focused electron-beam-induced deposition both experimentally and theoretically. The spin ice cluster is composed of twelve interacting Co nanoislands grown directly on top of a high-resolution micro-Hall sensor. By employing micromagnetic simulations and a macrospin model, we calculate the magnetization and the experimentally investigated stray field emanating from a single nanoisland. The parameters determined from a comparison with the experimental hysteresis loop are used to derive an effective single-dipole macrospin model that allows us to investigate the dynamics of the spin ice cluster. Our model reproduces the experimentally observed non-deterministic sequences in the magnetization curves as well as the distinct temperature dependence of the hysteresis loop.

  10. Melting behaviour of gold-platinum nanoalloy clusters by molecular dynamics simulations

    Energy Technology Data Exchange (ETDEWEB)

    Ong, Yee Pin; Yoon, Tiem Leong [School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Lim, Thong Leng [Faculty of Engineering and Technology, Multimedia University, Melaka Campus, 75450 Melaka (Malaysia)

    2015-04-24

    The melting behavior of bimetallic gold-platinum nanoclusters is studied by applying Brownian-type isothermal molecular dynamics (MD) simulation, a program modified from the cubic coupling scheme (CCS). The process begins with the ground-state structures obtained from global minimum search algorithm and proceeds with the investigation of the effect of temperature on the thermal properties of gold-platinum nanoalloy clusters. N-body Gupta potential has been employed in order to account for the interactions between gold and platinum atoms. The ground states of the nanoalloy clusters, which are core-shell segregated, are heated until they become thermally segregated. The detailed melting mechanism of the nanoalloy clusters is studied via this approach to provide insight into the thermal stability of the nanoalloy clusters.

  11. The Distributed Diagonal Force Decomposition Method for Parallelizing Molecular Dynamics Simulations

    Science.gov (United States)

    Boršnik, Urban; Miller, Benjamin T.; Brooks, Bernard R.; Janežič, Dušanka

    2011-01-01

    Parallelization is an effective way to reduce the computational time needed for molecular dynamics simulations. We describe a new parallelization method, the distributed-diagonal force decomposition method, with which we extend and improve the existing force decomposition methods. Our new method requires less data communication during molecular dynamics simulations than replicated data and current force decomposition methods, increasing the parallel efficiency. It also dynamically load-balances the processors' computational load throughout the simulation. The method is readily implemented in existing molecular dynamics codes and it has been incorporated into the CHARMM program, allowing its immediate use in conjunction with the many molecular dynamics simulation techniques that are already present in the program. We also present the design of the Force Decomposition Machine, a cluster of personal computers and networks that is tailored to running molecular dynamics simulations using the distributed diagonal force decomposition method. The design is expandable and provides various degrees of fault resilience. This approach is easily adaptable to computers with Graphics Processing Units because it is independent of the processor type being used. PMID:21793007

  12. Semiclassical Hybrid Approach to Condensed Phase Molecular Dynamics: Application to the I2Kr17 Cluster

    Czech Academy of Sciences Publication Activity Database

    Buchholz, M.; Goletz, Ch. M.; Grossman, F.; Schmidt, B.; Heyda, J.; Jungwirth, Pavel

    2012-01-01

    Roč. 116, č. 46 (2012), s. 11199-11210 ISSN 1089-5639 R&D Projects: GA ČR GBP208/12/G016 Institutional support: RVO:61388963 Keywords : semiclassical molecular dynamics * cluster * wavepacket * coherence * spectra Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.771, year: 2012

  13. PoD: dynamically create and use remote PROOF clusters. A thin client concept.

    CERN Multimedia

    CERN. Geneva

    2012-01-01

    PoD’s newly developed “pod-remote” command made it possible for users to utilize a thin client concept. In order to create dynamic PROOF clusters, users are now able to select a remote computer, even behind a firewall, to control a PoD server on...

  14. Oxidation of ligand-protected aluminum clusters: An ab initio molecular dynamics study

    International Nuclear Information System (INIS)

    Alnemrat, Sufian; Hooper, Joseph P.

    2014-01-01

    We report Car-Parrinello molecular dynamics simulations of the oxidation of ligand-protected aluminum clusters that form a prototypical cluster-assembled material. These clusters contain a small aluminum core surrounded by a monolayer of organic ligand. The aromatic cyclopentadienyl ligands form a strong bond with surface Al atoms, giving rise to an organometallic cluster that crystallizes into a low-symmetry solid and is briefly stable in air before oxidizing. Our calculations of isolated aluminum/cyclopentadienyl clusters reacting with oxygen show minimal reaction between the ligand and O 2 molecules at simulation temperatures of 500 and 1000 K. In all cases, the reaction pathway involves O 2 diffusing through the ligand barrier, splitting into atomic oxygen upon contact with the aluminum, and forming an oxide cluster with aluminum/ligand bonds still largely intact. Loss of individual aluminum-ligand units, as expected from unimolecular decomposition calculations, is not observed except following significant oxidation. These calculations highlight the role of the ligand in providing a steric barrier against oxidizers and in maintaining the large aluminum surface area of the solid-state cluster material

  15. Analyzing Dynamic Probabilistic Risk Assessment Data through Topology-Based Clustering

    Energy Technology Data Exchange (ETDEWEB)

    Diego Mandelli; Dan Maljovec; BeiWang; Valerio Pascucci; Peer-Timo Bremer

    2013-09-01

    We investigate the use of a topology-based clustering technique on the data generated by dynamic event tree methodologies. The clustering technique we utilizes focuses on a domain-partitioning algorithm based on topological structures known as the Morse-Smale complex, which partitions the data points into clusters based on their uniform gradient flow behavior. We perform both end state analysis and transient analysis to classify the set of nuclear scenarios. We demonstrate our methodology on a dataset generated for a sodium-cooled fast reactor during an aircraft crash scenario. The simulation tracks the temperature of the reactor as well as the time for a recovery team to fix the passive cooling system. Combined with clustering results obtained previously through mean shift methodology, we present the user with complementary views of the data that help illuminate key features that may be otherwise hidden using a single methodology. By clustering the data, the number of relevant test cases to be selected for further analysis can be drastically reduced by selecting a representative from each cluster. Identifying the similarities of simulations within a cluster can also aid in the drawing of important conclusions with respect to safety analysis.

  16. The Not So Simple Globular Cluster ω Cen. I. Spatial Distribution of the Multiple Stellar Populations

    Energy Technology Data Exchange (ETDEWEB)

    Calamida, A.; Saha, A. [National Optical Astronomy Observatory—AURA, 950 N Cherry Avenue, Tucson, AZ, 85719 (United States); Strampelli, G.; Rest, A. [Space Telescope Science Institute—AURA, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Bono, G.; Ferraro, I.; Iannicola, G. [INAF—Osservatorio Astronomico di Roma—Via Frascati 33, I-00040, Monteporzio Catone, Rome (Italy); Scolnic, D. [The University of Chicago, The Kavli Institute for Cosmological Physics, William Eckhardt Research Center—Suite 499, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); James, D.; Smith, C.; Zenteno, A., E-mail: calamida@noao.edu [Cerro Tololo Inter-American Observatory, Casilla 603, La Serena (Chile)

    2017-04-01

    We present a multi-band photometric catalog of ≈1.7 million cluster members for a field of view of ≈2° × 2° across ω Cen. Photometry is based on images collected with the Dark Energy Camera on the 4 m Blanco telescope and the Advanced Camera for Surveys on the Hubble Space Telescope . The unprecedented photometric accuracy and field coverage allowed us, for the first time, to investigate the spatial distribution of ω Cen multiple populations from the core to the tidal radius, confirming its very complex structure. We found that the frequency of blue main-sequence stars is increasing compared to red main-sequence stars starting from a distance of ≈25′ from the cluster center. Blue main-sequence stars also show a clumpy spatial distribution, with an excess in the northeast quadrant of the cluster pointing toward the direction of the Galactic center. Stars belonging to the reddest and faintest red-giant branch also show a more extended spatial distribution in the outskirts of ω Cen, a region never explored before. Both these stellar sub-populations, according to spectroscopic measurements, are more metal-rich compared to the cluster main stellar population. These findings, once confirmed, make ω Cen the only stellar system currently known where metal-rich stars have a more extended spatial distribution compared to metal-poor stars. Kinematic and chemical abundance measurements are now needed for stars in the external regions of ω Cen to better characterize the properties of these sub-populations.

  17. Molecular diagnostics based on clustering dynamics of magnetic nanobeads

    DEFF Research Database (Denmark)

    Donolato, Marco; Bejhed, Rebecca S.; de la Torre, Teresa Zardán Gómez

    2014-01-01

    or on the polymerase chain reaction (PCR) [1]. In this work we demonstrate detection of DNA coils formed from a Vibrio Cholerae DNA target at pM concentrations using a novel opto-magnetic approach exploiting the dynamic collective behavior of magnetic nanobeads. The technique relies on measurements of the light...... transmission modulation caused by the AC magnetic field-stimulated reversible formation and disruption of elongated MNB supra-structures during a cycle of the uniaxial applied magnetic field. As a specific clinically relevant diagnostic case, we detect DNA coils formed via padlock probe recognition...... and isothermal rolling circle amplification from Vibrio cholerae DNA. The detection method is shown in Figure 1. MNBs which specifically bind to the micrometric sized DNA coil cannot rotate under the field action as free beads and form chains; this results in a strongly modified opto-magnetic signal. As a core...

  18. Fast distributed large-pixel-count hologram computation using a GPU cluster.

    Science.gov (United States)

    Pan, Yuechao; Xu, Xuewu; Liang, Xinan

    2013-09-10

    Large-pixel-count holograms are one essential part for big size holographic three-dimensional (3D) display, but the generation of such holograms is computationally demanding. In order to address this issue, we have built a graphics processing unit (GPU) cluster with 32.5 Tflop/s computing power and implemented distributed hologram computation on it with speed improvement techniques, such as shared memory on GPU, GPU level adaptive load balancing, and node level load distribution. Using these speed improvement techniques on the GPU cluster, we have achieved 71.4 times computation speed increase for 186M-pixel holograms. Furthermore, we have used the approaches of diffraction limits and subdivision of holograms to overcome the GPU memory limit in computing large-pixel-count holograms. 745M-pixel and 1.80G-pixel holograms were computed in 343 and 3326 s, respectively, for more than 2 million object points with RGB colors. Color 3D objects with 1.02M points were successfully reconstructed from 186M-pixel hologram computed in 8.82 s with all the above three speed improvement techniques. It is shown that distributed hologram computation using a GPU cluster is a promising approach to increase the computation speed of large-pixel-count holograms for large size holographic display.

  19. Locality-Aware Request Distribution in Cluster-Based Network Servers

    OpenAIRE

    Pai, V.S.; Aron, M.; Banga, G.; Svendsen, M.; Druschel, P.; Zwaenepoel, W.; Nahum, E.

    1998-01-01

    We consider cluster-based network servers in which a front-end directs incoming requests to one of a number of back-ends. Specifically, we consider content-based request distribution: the front-end uses the content requested, in addition to information about the load on the back-end nodes, to choose which back-end will handle this request. Content-based request distribution can improve locality in the back-ends’ main memory caches, increase secondary storage scalability by partitioning the se...

  20. The size distribution of spatiotemporal extreme rainfall clusters around the globe

    Science.gov (United States)

    Traxl, D.; Boers, N.; Rheinwalt, A.; Goswami, B.; Kurths, J.

    2016-09-01

    The scaling behavior of rainfall has been extensively studied both in terms of event magnitudes and in terms of spatial extents of the events. Different heavy-tailed distributions have been proposed as candidates for both instances, but statistically rigorous treatments are rare. Here we combine the domains of event magnitudes and event area sizes by a spatiotemporal integration of 3-hourly rain rates corresponding to extreme events derived from the quasi-global high-resolution rainfall product Tropical Rainfall Measuring Mission 3B42. A maximum likelihood evaluation reveals that the distribution of spatiotemporally integrated extreme rainfall cluster sizes over the oceans is best described by a truncated power law, calling into question previous statements about scale-free distributions. The observed subpower law behavior of the distribution's tail is evaluated with a simple generative model, which indicates that the exponential truncation of an otherwise scale-free spatiotemporal cluster size distribution over the oceans could be explained by the existence of land masses on the globe.

  1. An Optimization Framework for Dynamic, Distributed Real-Time Systems

    Science.gov (United States)

    Eckert, Klaus; Juedes, David; Welch, Lonnie; Chelberg, David; Bruggerman, Carl; Drews, Frank; Fleeman, David; Parrott, David; Pfarr, Barbara

    2003-01-01

    Abstract. This paper presents a model that is useful for developing resource allocation algorithms for distributed real-time systems .that operate in dynamic environments. Interesting aspects of the model include dynamic environments, utility and service levels, which provide a means for graceful degradation in resource-constrained situations and support optimization of the allocation of resources. The paper also provides an allocation algorithm that illustrates how to use the model for producing feasible, optimal resource allocations.

  2. Distributed Coordination of Fractional Dynamical Systems with Exogenous Disturbances

    Directory of Open Access Journals (Sweden)

    Hongyong Yang

    2014-01-01

    Full Text Available Distributed coordination of fractional multiagent systems with external disturbances is studied. The state observer of fractional dynamical system is presented, and an adaptive pinning controller is designed for a little part of agents in multiagent systems without disturbances. This adaptive pinning controller with the state observer can ensure multiple agents' states reaching an expected reference tracking. Based on disturbance observers, the controllers are composited with the pinning controller and the state observer. By applying the stability theory of fractional order dynamical systems, the distributed coordination of fractional multiagent systems with external disturbances can be reached asymptotically.

  3. The model of drugs distribution dynamics in biological tissue

    Science.gov (United States)

    Ginevskij, D. A.; Izhevskij, P. V.; Sheino, I. N.

    2017-09-01

    The dose distribution by Neutron Capture Therapy follows the distribution of 10B in the tissue. The modern models of pharmacokinetics of drugs describe the processes occurring in conditioned "chambers" (blood-organ-tumor), but fail to describe the spatial distribution of the drug in the tumor and in normal tissue. The mathematical model of the spatial distribution dynamics of drugs in the tissue, depending on the concentration of the drug in the blood, was developed. The modeling method is the representation of the biological structure in the form of a randomly inhomogeneous medium in which the 10B distribution occurs. The parameters of the model, which cannot be determined rigorously in the experiment, are taken as the quantities subject to the laws of the unconnected random processes. The estimates of 10B distribution preparations in the tumor and healthy tissue, inside/outside the cells, are obtained.

  4. First Results on the Cluster Galaxy Population from the Subaru Hyper Suprime-Cam Survey. III. Brightest Cluster Galaxies, Stellar Mass Distribution, and Active Galaxies

    Science.gov (United States)

    Lin, Yen-Ting; Hsieh, Bau-Ching; Lin, Sheng-Chieh; Oguri, Masamune; Chen, Kai-Feng; Tanaka, Masayuki; Chiu, I.-Non; Huang, Song; Kodama, Tadayuki; Leauthaud, Alexie; More, Surhud; Nishizawa, Atsushi J.; Bundy, Kevin; Lin, Lihwai; Miyazaki, Satoshi

    2017-12-01

    The unprecedented depth and area surveyed by the Subaru Strategic Program with the Hyper Suprime-Cam (HSC-SSP) have enabled us to construct and publish the largest distant cluster sample out to z∼ 1 to date. In this exploratory study of cluster galaxy evolution from z = 1 to z = 0.3, we investigate the stellar mass assembly history of brightest cluster galaxies (BCGs), the evolution of stellar mass and luminosity distributions, the stellar mass surface density profile, as well as the population of radio galaxies. Our analysis is the first high-redshift application of the top N richest cluster selection, which is shown to allow us to trace the cluster galaxy evolution faithfully. Over the 230 deg2 area of the current HSC-SSP footprint, selecting the top 100 clusters in each of the four redshift bins allows us to observe the buildup of galaxy population in descendants of clusters whose z≈ 1 mass is about 2× {10}14 {M}ȯ . Our stellar mass is derived from a machine-learning algorithm, which is found to be unbiased and accurate with respect to the COSMOS data. We find very mild stellar mass growth in BCGs (about 35% between z = 1 and 0.3), and no evidence for evolution in both the total stellar mass–cluster mass correlation and the shape of the stellar mass surface density profile. We also present the first measurement of the radio luminosity distribution in clusters out to z∼ 1, and show hints of changes in the dominant accretion mode powering the cluster radio galaxies at z∼ 0.8.

  5. Dynamic scaling of ferromagnetic micro-rod clusters under a weak magnetic field.

    Science.gov (United States)

    Cheng, Rui; Zhu, Lu; Huang, Weijie; Mao, Leidong; Zhao, Yiping

    2016-10-12

    A controlled configurational change of micro-clusters in suspensions is essential for many smart material applications. In this paper, the dynamic process of ferromagnetic microrod clusters (FMRCs) under an external magnetic field was studied as a function of the cluster size N and the applied field B. The FMRCs rearranged from a side-by-side raft-like structure to an end-to-end chain-like structure, originating from coupled motions through the field-driven alignment of both ferromagnetic microrods and FMRCs. A theoretical model based on an extension of a zig-zag chain was developed, and both the cluster length and orientation could be characterized by a retardation time constant τ, with a relationship τ ∼ N 2 /B, which agrees well with the experimental results, τ ∼ N 2.2±0.2 /B 0.8±0.1 . Such a model can be used to predict other cluster dynamics or the magneto-elastic behavior of other soft matters consisting of FMRCs.

  6. Measurements of the gas temperature and iron abundance distribution in the Coma Cluster

    Science.gov (United States)

    Hughes, John P.; Gorenstein, P.; Fabricant, D.

    1988-01-01

    The medium energy X-ray detectors onboard the EXOSAT Observatory have been used to determine the gas temperature at several positions in the Coma Cluster of galaxies. Evidence is found at greater than 95 percent confidence for a higher temperature in the center of the cluster than in a position approximately 45 arcmin off-center. No difference in iron abundance is observed between the center and off-center regions and the equilibrium model for the distribution of elements in the Coma Cluster of Abramopoulos, Chanan, and Ku can be rejected with greater than 99.5 percent confidence, in favor of a model with more uniform composition. A phenomenological model is presented of the Coma Cluster, which is consistent with the data presented here, as well as the imaging data from the Einstein Observatory and the Tenma X-ray spectrum. The model has a central isothermal region of temperature about 9 keV extending to about 25 arcmin (about 1 Mpc). Beyond this radius the temperature falls as a polytrope with index about 1.6.

  7. Novel approaches to pin cluster synchronization on complex dynamical networks in Lur'e forms

    Science.gov (United States)

    Tang, Ze; Park, Ju H.; Feng, Jianwen

    2018-04-01

    This paper investigates the cluster synchronization of complex dynamical networks consisted of identical or nonidentical Lur'e systems. Due to the special topology structure of the complex networks and the existence of stochastic perturbations, a kind of randomly occurring pinning controller is designed which not only synchronizes all Lur'e systems in the same cluster but also decreases the negative influence among different clusters. Firstly, based on an extended integral inequality, the convex combination theorem and S-procedure, the conditions for cluster synchronization of identical Lur'e networks are derived in a convex domain. Secondly, randomly occurring adaptive pinning controllers with two independent Bernoulli stochastic variables are designed and then sufficient conditions are obtained for the cluster synchronization on complex networks consisted of nonidentical Lur'e systems. In addition, suitable control gains for successful cluster synchronization of nonidentical Lur'e networks are acquired by designing some adaptive updating laws. Finally, we present two numerical examples to demonstrate the validity of the control scheme and the theoretical analysis.

  8. Electron and nuclear dynamics of molecular clusters in ultraintense laser fields. IV. Coulomb explosion of molecular heteroclusters.

    Science.gov (United States)

    Last, Isidore; Jortner, Joshua

    2004-11-01

    In this paper we present a theoretical and computational study of the temporal dynamics and energetics of Coulomb explosion of (CD4)(n) and (CH4)(n) (n=55-4213) molecular heteroclusters in ultraintense (I=10(16)-10(19) W cm(-2)) laser fields, addressing the manifestation of electron dynamics, together with nuclear energetic and kinematic effects on the heterocluster Coulomb instability. The manifestations of the coupling between electron and nuclear dynamics were explored by molecular dynamics simulations for these heteroclusters coupled to Gaussian laser fields (pulse width tau=25 fs), elucidating outer ionization dynamics, nanoplasma screening effects (being significant for Icharges and masses. Nonuniform heterocluster Coulomb explosion (eta >1) manifests an overrun effect of the light ions relative to the heavy ions, exhibiting the expansion of two spatially separated subclusters, with the light ions forming the outer subcluster at the outer edge of the spatial distribution. Important features of the energetics of heterocluster Coulomb explosion originate from energetic triggering effects of the driving of the light ions by the heavy ions (C(4+) for I=10(17)-10(18) W cm(-2) and C(6+) for I=10(19) W cm(-2)), as well as for kinematic effects. Based on the CVI assumption, scaling laws for the cluster size (radius R(0)) dependence of the energetics of uniform Coulomb explosion of heteroclusters (eta=1) were derived, with the size dependence of the average (E(j,av)) and maximal (E(j,M)) ion energies being E(j,av)=aR(0) (2) and E(j,M)=(5a/3)R(0) (2), as well as for the ion energy distributions P(E(j)) proportional to E(j) (1/2); E(j)1) result in an isotope effect, predicting the enhancement (by 9%-11%) of E(H,av) for Coulomb explosion of (C(4+)H(4) (+))(eta) (eta=3) relative to E(D,av) for Coulomb explosion of (C(4+)D(4) (+))(eta) (eta=1.5), with the isotope effect being determined by the ratio of the kinematic parameters for the pair of Coulomb exploding clusters

  9. Ideal free distributions when resources undergo population dynamics

    Czech Academy of Sciences Publication Activity Database

    Křivan, Vlastimil

    2003-01-01

    Roč. 64, - (2003), s. 25-38 ISSN 0040-5809 R&D Projects: GA ČR GA201/03/0091; GA MŠk LA 101 Institutional research plan: CEZ:AV0Z5007907 Keywords : Predator -prey dynamics * ideal free distribution * optimal foraging Subject RIV: EH - Ecology, Behaviour Impact factor: 2.261, year: 2003

  10. Oscillation of second order neutral dynamic equations with distributed delay

    Directory of Open Access Journals (Sweden)

    Qiaoshun Yang

    2016-06-01

    Full Text Available In this paper, we establish new oscillation criteria for second order neutral dynamic equations with distributed delay by employing the generalized Riccati transformation. The obtained theorems essentially improve the oscillation results in the literature. And two examples are provided to illustrate to the versatility of our main results.

  11. Population dynamics and distribution of the coffee berry borer ...

    African Journals Online (AJOL)

    Population dynamics and distribution of coffee berry borer, Hypothenemus hampei (Ferrari) (Coleoptera: Scolytidae) were studied on Coffea arabica L. in southwestern region of Ethiopia. Thirty coffee trees were sampled at weekly intervals from 2000 to 2001. Findings of this study showed that coffee berry borer population ...

  12. A Dynamic Distributed Architecture for Temporal Data Abstraction

    OpenAIRE

    Chauhan, Vijay P.; O’Connor, Martin J.; Das, Amar K.

    2006-01-01

    Considerable work has been taken by researchers to address the need for temporal data deduction in biomedical applications, but relatively little research has examined how to create robust, efficient approaches for such methods using large databases. We present the design and evaluation of a distributed architecture that can be dynamically optimized to perform large-scale abstraction of temporal data.

  13. Distributed dynamic simulations of networked control and building performance applications.

    Science.gov (United States)

    Yahiaoui, Azzedine

    2018-02-01

    The use of computer-based automation and control systems for smart sustainable buildings, often so-called Automated Buildings (ABs), has become an effective way to automatically control, optimize, and supervise a wide range of building performance applications over a network while achieving the minimum energy consumption possible, and in doing so generally refers to Building Automation and Control Systems (BACS) architecture. Instead of costly and time-consuming experiments, this paper focuses on using distributed dynamic simulations to analyze the real-time performance of network-based building control systems in ABs and improve the functions of the BACS technology. The paper also presents the development and design of a distributed dynamic simulation environment with the capability of representing the BACS architecture in simulation by run-time coupling two or more different software tools over a network. The application and capability of this new dynamic simulation environment are demonstrated by an experimental design in this paper.

  14. Dynamical cluster approximation plus semiclassical approximation study for a Mott insulator and d-wave pairing

    Science.gov (United States)

    Kim, SungKun; Lee, Hunpyo

    2017-06-01

    Via a dynamical cluster approximation with N c = 4 in combination with a semiclassical approximation (DCA+SCA), we study the doped two-dimensional Hubbard model. We obtain a plaquette antiferromagnetic (AF) Mott insulator, a plaquette AF ordered metal, a pseudogap (or d-wave superconductor) and a paramagnetic metal by tuning the doping concentration. These features are similar to the behaviors observed in copper-oxide superconductors and are in qualitative agreement with the results calculated by the cluster dynamical mean field theory with the continuous-time quantum Monte Carlo (CDMFT+CTQMC) approach. The results of our DCA+SCA differ from those of the CDMFT+CTQMC approach in that the d-wave superconducting order parameters are shown even in the high doped region, unlike the results of the CDMFT+CTQMC approach. We think that the strong plaquette AF orderings in the dynamical cluster approximation (DCA) with N c = 4 suppress superconducting states with increasing doping up to strongly doped region, because frozen dynamical fluctuations in a semiclassical approximation (SCA) approach are unable to destroy those orderings. Our calculation with short-range spatial fluctuations is initial research, because the SCA can manage long-range spatial fluctuations in feasible computational times beyond the CDMFT+CTQMC tool. We believe that our future DCA+SCA calculations should supply information on the fully momentum-resolved physical properties, which could be compared with the results measured by angle-resolved photoemission spectroscopy experiments.

  15. BeoBLAST: distributed BLAST and PSI-BLAST on a Beowulf cluster.

    Science.gov (United States)

    Grant, J D; Dunbrack, R L; Manion, F J; Ochs, M F

    2002-05-01

    BeoBLAST is an integrated software package that handles user requests and distributes BLAST and PSI-BLAST searches to nodes of a Beowulf cluster, thus providing a simple way to implement a scalable BLAST system on top of relatively inexpensive computer clusters. Additionally, BeoBLAST offers a number of novel search features through its web interface, including the ability to perform simultaneous searches of multiple databases with multiple queries, and the ability to start a search using the PSSM generated from a previous PSI-BLAST search on a different database. The underlying system can also handle automated querying for high throughput work. Source code is available under the GNU public license at http://bioinformatics.fccc.edu/

  16. Multi-party Measurement-Device-Independent Quantum Key Distribution Based on Cluster States

    Science.gov (United States)

    Liu, Chuanqi; Zhu, Changhua; Ma, Shuquan; Pei, Changxing

    2018-03-01

    We propose a novel multi-party measurement-device-independent quantum key distribution (MDI-QKD) protocol based on cluster states. A four-photon analyzer which can distinguish all the 16 cluster states serves as the measurement device for four-party MDI-QKD. Any two out of four participants can build secure keys after the analyzers obtains successful outputs and the two participants perform post-processing. We derive a security analysis for the protocol, and analyze the key rates under different values of polarization misalignment. The results show that four-party MDI-QKD is feasible over 280 km in the optical fiber channel when the key rate is about 10- 6 with the polarization misalignment parameter 0.015. Moreover, our work takes an important step toward a quantum communication network.

  17. Multi-party Measurement-Device-Independent Quantum Key Distribution Based on Cluster States

    Science.gov (United States)

    Liu, Chuanqi; Zhu, Changhua; Ma, Shuquan; Pei, Changxing

    2017-12-01

    We propose a novel multi-party measurement-device-independent quantum key distribution (MDI-QKD) protocol based on cluster states. A four-photon analyzer which can distinguish all the 16 cluster states serves as the measurement device for four-party MDI-QKD. Any two out of four participants can build secure keys after the analyzers obtains successful outputs and the two participants perform post-processing. We derive a security analysis for the protocol, and analyze the key rates under different values of polarization misalignment. The results show that four-party MDI-QKD is feasible over 280 km in the optical fiber channel when the key rate is about 10- 6 with the polarization misalignment parameter 0.015. Moreover, our work takes an important step toward a quantum communication network.

  18. Orientational distributions of contact clusters in proteins closely resemble those of an icosahedron.

    Science.gov (United States)

    Feng, Yaping; Jernigan, Robert L; Kloczkowski, Andrzej

    2008-11-15

    The orientational geometry of residue packing in proteins was studied in the past by superimposing clusters of neighboring residues with several simple lattices (Bagci et al., Proteins 2003;53:56-67; Raghunathan et al., Protein Sci 1997;6:2072-2083). In this work, instead of a lattice we use the regular polyhedron, the icosahedron, as the model to describe the orientational distribution of contacts in clusters derived from a high-resolution protein dataset (522 protein structures with high resolution icosahedron is 0.91, which is a significant improvement in comparison with the value 0.82 for the order parameter with the face-centered cubic (fcc) lattice. Close packing tendencies and patterns of residue packing in proteins are considered in detail and a theoretical description of these packing regularities is proposed.

  19. Distributed Consensus-Based Control of Multiple DC-Microgrids Clusters

    DEFF Research Database (Denmark)

    Shafiee, Qobad; Dragicevic, Tomislav; Andrade, Fabio

    2014-01-01

    This paper presents consensus-based distributed control strategies for voltage regulation and power flow control of dc microgrid (MG) clusters. In the proposed strategy, primary level of control is used to regulate the common bus voltage inside each MG locally. An SOC-based adaptive droop method...... is introduced for this level which determines droop coefficient automatically, thus equalizing SOC of batteries inside each MG. In the secondary level, a distributed consensus based voltage control strategy is proposed to eliminate the average voltage deviation while guaranteeing proper regulation of power flow...... among the MGs. Using the consensus protocol, the global information can be accurately shared in a distributed way. This allows the power flow control to be achieved at the same time as it can be accomplished only at the cost of having the voltage differences inside the system. Similarly, a consensus...

  20. [Origination of Pareto distribution in complex dynamic systems].

    Science.gov (United States)

    Chernavskiĭ, D S; Nikitin, A P; Chernavskaia, O D

    2008-01-01

    The Pareto distribution, whose probability density function can be approximated at sufficiently great chi as rho(chi) - chi(-alpha), where alpha > or = 2, is of crucial importance from both the theoretical and practical point of view. The main reason is its qualitative distinction from the normal (Gaussian) distribution. Namely, the probability of high deviations appears to be significantly higher. The conception of the universal applicability of the Gauss law remains to be widely distributed despite the lack of objective confirmation of this notion in a variety of application areas. The origin of the Pareto distribution in dynamic systems located in the gaussian noise field is considered. A simple one-dimensional model is discussed where the system response in a rather wide interval of the variable can be quite precisely approximated by this distribution.

  1. The uniformity and time-invariance of the intra-cluster metal distribution in galaxy clusters from the IllustrisTNG simulations

    Science.gov (United States)

    Vogelsberger, Mark; Marinacci, Federico; Torrey, Paul; Genel, Shy; Springel, Volker; Weinberger, Rainer; Pakmor, Rüdiger; Hernquist, Lars; Naiman, Jill; Pillepich, Annalisa; Nelson, Dylan

    2018-02-01

    The distribution of metals in the intra-cluster medium (ICM) encodes important information about the enrichment history and formation of galaxy clusters. Here, we explore the metal content of clusters in IllustrisTNG - a new suite of galaxy formation simulations building on the Illustris project. Our cluster sample contains 20 objects in TNG100 - a ˜(100 Mpc)3 volume simulation with 2 × 18203 resolution elements, and 370 objects in TNG300 - a ˜(300 Mpc)3 volume simulation with 2 × 25003 resolution elements. The z = 0 metallicity profiles agree with observations, and the enrichment history is consistent with observational data going beyond z ˜ 1, showing nearly no metallicity evolution. The abundance profiles vary only minimally within the cluster samples, especially in the outskirts with a relative scatter of ˜ 15 per cent. The average metallicity profile flattens towards the centre, where we find a logarithmic slope of -0.1 compared to -0.5 in the outskirts. Cool core clusters have more centrally peaked metallicity profiles (˜0.8 solar) compared to non-cool core systems (˜0.5 solar), similar to observational trends. Si/Fe and O/Fe radial profiles follow positive gradients. The outer abundance profiles do not evolve below z ˜ 2, whereas the inner profiles flatten towards z = 0. More than ˜ 80 per cent of the metals in the ICM have been accreted from the proto-cluster environment, which has been enriched to ˜0.1 solar already at z ˜ 2. We conclude that the intra-cluster metal distribution is uniform among our cluster sample, nearly time-invariant in the outskirts for more than 10 Gyr, and forms through a universal enrichment history.

  2. Single Molecule Cluster Analysis Identifies Signature Dynamic Conformations along the Splicing Pathway

    Science.gov (United States)

    Blanco, Mario R.; Martin, Joshua S.; Kahlscheuer, Matthew L.; Krishnan, Ramya; Abelson, John; Laederach, Alain; Walter, Nils G.

    2016-01-01

    The spliceosome is the dynamic RNA-protein machine responsible for faithfully splicing introns from precursor messenger RNAs (pre-mRNAs). Many of the dynamic processes required for the proper assembly, catalytic activation, and disassembly of the spliceosome as it acts on its pre-mRNA substrate remain poorly understood, a challenge that persists for many biomolecular machines. Here, we developed a fluorescence-based Single Molecule Cluster Analysis (SiMCAn) tool to dissect the manifold conformational dynamics of a pre-mRNA through the splicing cycle. By clustering common dynamic behaviors derived from selectively blocked splicing reactions, SiMCAn was able to identify signature conformations and dynamic behaviors of multiple ATP-dependent intermediates. In addition, it identified a conformation adopted late in splicing by a 3′ splice site mutant, invoking a mechanism for substrate proofreading. SiMCAn presents a novel framework for interpreting complex single molecule behaviors that should prove widely useful for the comprehensive analysis of a plethora of dynamic cellular machines. PMID:26414013

  3. Age distribution dynamics with stochastic jumps in mortality.

    Science.gov (United States)

    Calabrese, Salvatore; Porporato, Amilcare; Laio, Francesco; D'Odorico, Paolo; Ridolfi, Luca

    2017-11-01

    While deterministic age distribution models have been extensively studied and applied in various disciplines, little work has been devoted to understanding the role of stochasticity in birth and mortality terms. In this paper, we analyse a stochastic M'Kendrick-von Foerster equation in which jumps in mortality represent intense losses of population due to external events. We present explicit solutions for the probability density functions of the age distribution and the total population and for the temporal dynamics of their moments. We also derive the dynamics of the mean age of the population and its harmonic mean. The framework is then used to calculate the age distribution of salt in the soil root zone, where the accumulation of salt by atmospheric deposition is counteracted by plant uptake and by jump losses due to percolation events.

  4. Distributed continuous energy scheduling for dynamic virtual power plants

    International Nuclear Information System (INIS)

    Niesse, Astrid

    2015-01-01

    This thesis presents DynaSCOPE as distributed control method for continuous energy scheduling for dynamic virtual power plants (DVPP). DVPPs aggregate the flexibility of distributed energy units to address current energy markets. As an extension of the Virtual Power Plant concept they show high dynamics in aggregation and operation of energy units. Whereas operation schedules are set up for all energy units in a day-ahead planning procedure, incidents may render these schedules infeasible during execution, like deviation from prognoses or outages. Thus, a continuous scheduling process is needed to ensure product fulfillment. With DynaSCOPE, software agents representing single energy units solve this problem in a completely distributed heuristic approach. Using a stepped concept, several damping mechanisms are applied to allow minimum disturbance while continuously trying to fulfill the product as contracted at the market.

  5. Dynamic Power Tariff for Congestion Management in Distribution Networks

    DEFF Research Database (Denmark)

    Huang, Shaojun; Wu, Qiuwei; Shahidehpour, Mohammad

    2018-01-01

    This paper proposes dynamic power tariff (DPT), a new concept for congestion management in distribution networks with high penetration of electric vehicles (EVs), and heat pumps (HPs). The DPT concept is proposed to overcome a drawback of the dynamic tariff (DT) method, i.e., DPT can replace...... the price sensitivity parameter in the DT method, which is relatively unrealistic in practice. Based on the control theory, a control model with two control loops, i.e., the power flow control and voltage control, is established to analyze the congestion management process by the DPT method. Furthermore......, an iterative method based on distributed optimization is proposed to determine the DPT rates, which enables active participation of aggregators in the congestion management. The case studies demonstrate the efficacy of the DPT method for congestion management in distribution networks, and show its ability...

  6. Comparing cluster-level dynamic treatment regimens using sequential, multiple assignment, randomized trials: Regression estimation and sample size considerations.

    Science.gov (United States)

    NeCamp, Timothy; Kilbourne, Amy; Almirall, Daniel

    2017-08-01

    Cluster-level dynamic treatment regimens can be used to guide sequential treatment decision-making at the cluster level in order to improve outcomes at the individual or patient-level. In a cluster-level dynamic treatment regimen, the treatment is potentially adapted and re-adapted over time based on changes in the cluster that could be impacted by prior intervention, including aggregate measures of the individuals or patients that compose it. Cluster-randomized sequential multiple assignment randomized trials can be used to answer multiple open questions preventing scientists from developing high-quality cluster-level dynamic treatment regimens. In a cluster-randomized sequential multiple assignment randomized trial, sequential randomizations occur at the cluster level and outcomes are observed at the individual level. This manuscript makes two contributions to the design and analysis of cluster-randomized sequential multiple assignment randomized trials. First, a weighted least squares regression approach is proposed for comparing the mean of a patient-level outcome between the cluster-level dynamic treatment regimens embedded in a sequential multiple assignment randomized trial. The regression approach facilitates the use of baseline covariates which is often critical in the analysis of cluster-level trials. Second, sample size calculators are derived for two common cluster-randomized sequential multiple assignment randomized trial designs for use when the primary aim is a between-dynamic treatment regimen comparison of the mean of a continuous patient-level outcome. The methods are motivated by the Adaptive Implementation of Effective Programs Trial which is, to our knowledge, the first-ever cluster-randomized sequential multiple assignment randomized trial in psychiatry.

  7. Using Dynamic Quantum Clustering to Analyze Hierarchically Heterogeneous Samples on the Nanoscale

    Energy Technology Data Exchange (ETDEWEB)

    Hume, Allison; /Princeton U. /SLAC

    2012-09-07

    Dynamic Quantum Clustering (DQC) is an unsupervised, high visual data mining technique. DQC was tested as an analysis method for X-ray Absorption Near Edge Structure (XANES) data from the Transmission X-ray Microscopy (TXM) group. The TXM group images hierarchically heterogeneous materials with nanoscale resolution and large field of view. XANES data consists of energy spectra for each pixel of an image. It was determined that DQC successfully identifies structure in data of this type without prior knowledge of the components in the sample. Clusters and sub-clusters clearly reflected features of the spectra that identified chemical component, chemical environment, and density in the image. DQC can also be used in conjunction with the established data analysis technique, which does require knowledge of components present.

  8. Molecular dynamics computer simulation study of Pdn (n=13, 19, 38 and 55) clusters

    International Nuclear Information System (INIS)

    Karabacak, M.; Oezcelik, S.; Guevenc, Z.B.

    2002-01-01

    Using constant-energy molecular dynamics and thermal quenching simulations, we have studied minimum-energy structures and energetics, Pd n (n=13, 19, 38, and 55) clusters employing the Voter and Chen's version of parameterisation of the embedded-atom potential surface. Isomer statistics for Pdn ( n = 13 and 19 ) is obtained from 10000 initial independent configurations, which have been generated along high-energy trajectories (chosen energy values are high enough to melt the clusters). The thermal quenching technique is employed to remove the internal kinetic energy of the clusters. The locally stable isomers are separated from metastable ones. Probabilities belonging to sampling the basins of attractions of each isomers are computed, and then, isomers' energy spectra are analyzed

  9. Signature of non-isotropic distribution of stellar rotation inclination angles in the Praesepe cluster

    Science.gov (United States)

    Kovacs, Geza

    2018-04-01

    The distribution of the stellar rotation axes of 113 main sequence stars in the open cluster Praesepe are examined by using current photometric rotation periods, spectroscopic rotation velocities, and estimated stellar radii. Three different samples of stellar rotation data on spotted stars from the Galactic field and two independent samples of planetary hosts are used as control samples to support the consistency of the analysis. Considering the high completeness of the Praesepe sample and the behavior of the control samples, we find that the main sequence F - K stars in this cluster are susceptible to rotational axis alignment. Using a cone model, the most likely inclination angle is 76° ± 14° with a half opening angle of 47° ± 24°. Non-isotropic distribution of the inclination angles is preferred over the isotropic distribution, except if the rotation velocities used in this work are systematically overestimated. We found no indication of this being the case on the basis of the currently available data. Data are only available at the CDS, together with the other two compiled datasets used in this paper, via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/612/L2

  10. Spatial clustering in the spatio-temporal dynamics of endemic cholera

    Directory of Open Access Journals (Sweden)

    Emch Michael

    2010-03-01

    Full Text Available Abstract Background The spatio-temporal patterns of infectious diseases that are environmentally driven reflect the combined effects of transmission dynamics and environmental heterogeneity. They contain important information on different routes of transmission, including the role of environmental reservoirs. Consideration of the spatial component in infectious disease dynamics has led to insights on the propagation of fronts at the level of counties in rabies in the US, and the metapopulation behavior at the level of cities in childhood diseases such as measles in the UK, both at relatively coarse scales. As epidemiological data on individual infections become available, spatio-temporal patterns can be examined at higher resolutions. Methods The extensive spatio-temporal data set for cholera in Matlab, Bangladesh, maps the individual location of cases from 1983 to 2003. This unique record allows us to examine the spatial structure of cholera outbreaks, to address the role of primary transmission, occurring from an aquatic reservoir to the human host, and that of secondary transmission, involving a feedback between current and past levels of infection. We use Ripley's K and L indices and bootstrapping methods to evaluate the occurrence of spatial clustering in the cases during outbreaks using different temporal windows. The spatial location of cases was also confronted against the spatial location of water sources. Results Spatial clustering of cholera cases was detected at different temporal and spatial scales. Cases relative to water sources also exhibit spatial clustering. Conclusions The clustering of cases supports an important role of secondary transmission in the dynamics of cholera epidemics in Matlab, Bangladesh. The spatial clustering of cases relative to water sources, and its timing, suggests an effective role of water reservoirs during the onset of cholera outbreaks. Once primary transmission has initiated an outbreak, secondary

  11. Spherical Harmonic Analysis of Particle Velocity Distribution Function: Comparison of Moments and Anisotropies using Cluster Data

    Science.gov (United States)

    Gurgiolo, Chris; Vinas, Adolfo F.

    2009-01-01

    This paper presents a spherical harmonic analysis of the plasma velocity distribution function using high-angular, energy, and time resolution Cluster data obtained from the PEACE spectrometer instrument to demonstrate how this analysis models the particle distribution function and its moments and anisotropies. The results show that spherical harmonic analysis produced a robust physical representation model of the velocity distribution function, resolving the main features of the measured distributions. From the spherical harmonic analysis, a minimum set of nine spectral coefficients was obtained from which the moment (up to the heat flux), anisotropy, and asymmetry calculations of the velocity distribution function were obtained. The spherical harmonic method provides a potentially effective "compression" technique that can be easily carried out onboard a spacecraft to determine the moments and anisotropies of the particle velocity distribution function for any species. These calculations were implemented using three different approaches, namely, the standard traditional integration, the spherical harmonic (SPH) spectral coefficients integration, and the singular value decomposition (SVD) on the spherical harmonic methods. A comparison among the various methods shows that both SPH and SVD approaches provide remarkable agreement with the standard moment integration method.

  12. Smoluchowski coagulation models of sea ice thickness distribution dynamics

    Science.gov (United States)

    Godlovitch, D.; Illner, R.; Monahan, A.

    2011-12-01

    Sea ice thickness distributions display a ubiquitous exponential decrease with thickness. This tail characterizes the range of ice thickness produced by mechanical redistribution of ice through the process of ridging, rafting, and shearing. We investigate how well the thickness distribution can be simulated by representing mechanical redistribution as a generalized stacking process. Such processes are naturally described by a well-studied class of models known as Smoluchowski Coagulation Models (SCMs), which describe the dynamics of a population of fixed-mass "particles" which combine in pairs to form a "particle" with the combined mass of the constituent pair at a rate which depends on the mass of the interacting particles. Like observed sea ice thickness distributions, the mass distribution of the populations generated by SCMs has an exponential or quasi-exponential form. We use SCMs to model sea ice, identifying mass-increasing particle combinations with thickness-increasing ice redistribution processes. Our model couples an SCM component with a thermodynamic component and generates qualitatively accurate thickness distributions with a variety of rate kernels. Our results suggest that the exponential tail of the sea ice thickness distribution arises from the nature of the ridging process, rather than specific physical properties of sea ice or the spatial arrangement of floes, and that the relative strengths of the dynamic and thermodynamic processes are key in accurately simulating the rate at which the sea ice thickness tail drops off with thickness.

  13. Dynamics of photoprocesses induced by femtosecond infrared radiation in free molecules and clusters of iron pentacarbonyl

    International Nuclear Information System (INIS)

    Kompanets, V. O.; Lokhman, V. N.; Poydashev, D. G.; Chekalin, S. V.; Ryabov, E. A.

    2016-01-01

    The dynamics of photoprocesses induced by femtosecond infrared radiation in free Fe(CO) 5 molecules and their clusters owing to the resonant excitation of vibrations of CO bonds in the 5-μm range has been studied. The technique of infrared excitation and photoionization probing (λ = 400 nm) by femtosecond pulses has been used in combination with time-of-flight mass spectrometry. It has been found that an infrared pulse selectively excites vibrations of CO bonds in free molecules, which results in a decrease in the yield of the Fe(CO) 5 + molecular ion. Subsequent relaxation processes have been analyzed and the results have been interpreted. The time of the energy transfer from excited vibrations to other vibrations of the molecule owing to intramolecular relaxation has been measured. The dynamics of dissociation of [Fe(CO) 5 ] n clusters irradiated by femtosecond infrared radiation has been studied. The time dependence of the yield of free molecules has been measured under different infrared laser excitation conditions. We have proposed a model that well describes the results of the experiment and makes it possible, in particular, to calculate the profile of variation of the temperature of clusters within the “evaporation ensemble” concept. The intramolecular and intracluster vibrational relaxation rates in [Fe(CO) 5 ] n clusters have been estimated.

  14. Dynamics of Brokerage Positions in Clusters: Evidence from the Spanish Foodstuffs Industry

    Directory of Open Access Journals (Sweden)

    José Antonio Belso-Martínez

    2017-02-01

    Full Text Available Shifting away from traditional approaches orientated towards the analysis of the benefits associated with brokerage, this paper provides valuable insights into the dynamics of this network position and the opportunities to innovate that it provides. Using fine grain micro data collected in a foodstuff Spanish cluster, the evolution of different brokerage profiles is analyzed in depth. It was particularly evident how firm-level characteristics (status, former mediating experience and external openness and their interactions may generate changes in the different brokerage roles over a period of time. The findings of this work partially validate expectations based on the network dynamics approaches. Status and previous mediating experience facilitate the creation of partnerships, fostering brokerage. Conversely, interaction effects demote brokerage activity at the intra-cluster level, suggesting the selective nature of brokers’ relational behavior.

  15. Dynamic quantum clustering: a tool for visual exploration of structures in data

    Energy Technology Data Exchange (ETDEWEB)

    Weinstein, Marvin; /SLAC; Horn, David; /Tel Aviv U.

    2009-10-17

    A given set of data-points in some feature space may be associated with a Schroedinger equation whose potential is determined by the data. This is known to lead to good clustering solutions. Here we extend this approach into a full-fledged dynamical scheme using a time-dependent Schroedinger equation. Moreover, we approximate this Hamiltonian formalism by a truncated calculation within a set of Gaussian wave functions (coherent states) centered around the original points. This allows for analytic evaluation of the time evolution of all such states, opening up the possibility of exploration of relationships among data-points through observation of varying dynamical-distances among points and convergence of points into clusters. This formalism may be further supplemented by preprocessing, such as dimensional reduction through singular value decomposition or feature filtering.

  16. Dynamic Quantum Clustering: A Tool for Unsupervised Exploration of Structures in Data

    Energy Technology Data Exchange (ETDEWEB)

    Weinstein, Marvin; /SLAC; Horn, David; /Tel Aviv U.

    2008-10-30

    A given set of data-points in some feature space may be associated with a Schroedinger equation whose potential is determined by the data. This is known to lead to good clustering solutions. Here we extend this approach into a full-fledged dynamical scheme using a time-dependent Schroedinger equation with a small diffusion component. Moreover, we approximate this Hamiltonian formalism by a truncated calculation within a set of Gaussian wave functions (coherent states) centered around the original points. This allows for analytic evaluation of the time evolution of all such states, opening up the possibility of exploration of relationships among data-points through observation of varying dynamical-distances among points and convergence of points into clusters. This formalism may be further supplemented by preprocessing, such as dimensional reduction through singular value decomposition or feature filtering.

  17. Communication: Time-dependent optimized coupled-cluster method for multielectron dynamics

    Science.gov (United States)

    Sato, Takeshi; Pathak, Himadri; Orimo, Yuki; Ishikawa, Kenichi L.

    2018-02-01

    Time-dependent coupled-cluster method with time-varying orbital functions, called time-dependent optimized coupled-cluster (TD-OCC) method, is formulated for multielectron dynamics in an intense laser field. We have successfully derived the equations of motion for CC amplitudes and orthonormal orbital functions based on the real action functional, and implemented the method including double excitations (TD-OCCD) and double and triple excitations (TD-OCCDT) within the optimized active orbitals. The present method is size extensive and gauge invariant, a polynomial cost-scaling alternative to the time-dependent multiconfiguration self-consistent-field method. The first application of the TD-OCC method of intense-laser driven correlated electron dynamics in Ar atom is reported.

  18. Dynamic shared state maintenance in distributed virtual environments

    Science.gov (United States)

    Hamza-Lup, Felix George

    Advances in computer networks and rendering systems facilitate the creation of distributed collaborative environments in which the distribution of information at remote locations allows efficient communication. Particularly challenging are distributed interactive Virtual Environments (VE) that allow knowledge sharing through 3D information. The purpose of this work is to address the problem of latency in distributed interactive VE and to develop a conceptual model for consistency maintenance in these environments based on the participant interaction model. An area that needs to be explored is the relationship between the dynamic shared state and the interaction with the virtual entities present in the shared scene. Mixed Reality (MR) and VR environments must bring the human participant interaction into the loop through a wide range of electronic motion sensors, and haptic devices. Part of the work presented here defines a novel criterion for categorization of distributed interactive VE and introduces, as well as analyzes, an adaptive synchronization algorithm for consistency maintenance in such environments. As part of the work, a distributed interactive Augmented Reality (AR) testbed and the algorithm implementation details are presented. Currently the testbed is part of several research efforts at the Optical Diagnostics and Applications Laboratory including 3D visualization applications using custom built head-mounted displays (HMDs) with optical motion tracking and a medical training prototype for endotracheal intubation and medical prognostics. An objective method using quaternion calculus is applied for the algorithm assessment. In spite of significant network latency, results show that the dynamic shared state can be maintained consistent at multiple remotely located sites. In further consideration of the latency problems and in the light of the current trends in interactive distributed VE applications, we propose a hybrid distributed system architecture for

  19. Characterizing single-molecule FRET dynamics with probability distribution analysis.

    Science.gov (United States)

    Santoso, Yusdi; Torella, Joseph P; Kapanidis, Achillefs N

    2010-07-12

    Probability distribution analysis (PDA) is a recently developed statistical tool for predicting the shapes of single-molecule fluorescence resonance energy transfer (smFRET) histograms, which allows the identification of single or multiple static molecular species within a single histogram. We used a generalized PDA method to predict the shapes of FRET histograms for molecules interconverting dynamically between multiple states. This method is tested on a series of model systems, including both static DNA fragments and dynamic DNA hairpins. By fitting the shape of this expected distribution to experimental data, the timescale of hairpin conformational fluctuations can be recovered, in good agreement with earlier published results obtained using different techniques. This method is also applied to studying the conformational fluctuations in the unliganded Klenow fragment (KF) of Escherichia coli DNA polymerase I, which allows both confirmation of the consistency of a simple, two-state kinetic model with the observed smFRET distribution of unliganded KF and extraction of a millisecond fluctuation timescale, in good agreement with rates reported elsewhere. We expect this method to be useful in extracting rates from processes exhibiting dynamic FRET, and in hypothesis-testing models of conformational dynamics against experimental data.

  20. Two resource distribution strategies for dynamic mitigation of influenza pandemics

    Directory of Open Access Journals (Sweden)

    Andrés Uribe-Sánchez

    2010-07-01

    Full Text Available Andrés Uribe-Sánchez, Alex Savachkin1Department of Industrial and Management Systems Engineering University of South Florida, Tampa, FL 33620, USAAbstract: As recently pointed out by the Institute of Medicine, the existing pandemic ­containment and mitigation models lack the dynamic decision support capabilities. We ­present two simulation-based optimization models for developing dynamic predictive resource ­distribution strategies for cross-regional pandemic outbreaks. In both models, the underlying simulation mimics the disease and population dynamics of the affected regions. The quantity-based optimization model generates a progressive allocation of limited quantities of mitigation resources, including vaccines, antiviral, administration capacities, and social distancing enforcement resources. The budget-based optimization model strives instead allocating a total resource budget. Both models seek to minimize the impact of ongoing outbreaks and the expected impact of potential outbreaks. The models incorporate measures of morbidity, mortality, and social distancing, translated into the societal and economic costs of lost productivity and medical expenses. The models were calibrated using historic pandemic data and implemented on a sample outbreak in Florida, with over four million inhabitants. The quantity-based model was found to be inferior to the budget-based model, which was advantageous in its ability to balance the varying relative cost and effectiveness of individual resources. The models are intended to assist public health policy makers in developing effective distribution policies for mitigation of influenza pandemics.Keywords: pandemic, mitigation, distribution, dynamic, resources, budget

  1. On the radial distribution of white dwarfs in the Galactic globular cluster omega Cen

    Science.gov (United States)

    Calamida, A.; Corsi, C. E.; Bono, G.; Stetson, P. B.; Prada Moroni, P. G.; Degl'Innocenti, S.; Ferraro, I.; Iannicola, G.; Koester, D.; Pulone, L.; Monelli, M.; Amico, P.; Buonanno, R.; Freyhammer, L. M.; Marchetti, E.; Nonino, M.; Romaniello, M.

    We present deep and accurate photometry (F435W, F625W, F658N) of the Galactic Globular Cluster omega Cen collected with the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope (HST). We identified ≈ 6,500 white dwarf (WD) candidates and compared their radial distribution with that of Main Sequence (MS) stars. We found a mild evidence that young WDs ( 0.1 ≲ t ≲ 0.6 Gyr) are less centrally concentrated when compared to MS stars in the magnitude range 25 < F435W < 26.5.

  2. Parallel variable selection of molecular dynamics clusters as a tool for calculation of spectroscopic properties

    Czech Academy of Sciences Publication Activity Database

    Kessler, Jiří; Dračínský, Martin; Bouř, Petr

    2013-01-01

    Roč. 34, č. 5 (2013), s. 366-371 ISSN 0192-8651 R&D Projects: GA ČR GAP208/11/0105; GA MŠk(CZ) LH11033 Grant - others:GA MŠk(CZ) LM2010005 Institutional support: RVO:61388963 Keywords : molecular dynamics * clusters * density functional theory * Raman optical activity * NMR Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.601, year: 2013

  3. Spin dynamics study of magnetic molecular clusters by means of Moessbauer spectroscopy

    International Nuclear Information System (INIS)

    Cianchi, L.; Del Giallo, F.; Spina, G.; Reiff, W.; Caneschi, A.

    2002-01-01

    Spin dynamics of the two magnetic molecular clusters Fe4 and Fe8, with four and eight Fe(III) ions, respectively, was studied by means of Moessbauer spectroscopy. The transition probabilities W's between the spin states of the ground multiplet were obtained from the fitting of the spectra. For the Fe4 cluster we found that, in the range from 1.38 to 77 K, the trend of W's versus the temperature corresponds to an Orbach's process involving an excited state with energy of about 160 K. For the Fe8, which, due to the presence of a low-energy excited state, could not be studied at temperatures greater than 20 K, the trend of W's in the range from 4 to 18 K seems to correspond to a direct process. The correlation functions of the magnetization were then calculated in terms of the W's. They have an exponential trend for the Fe4 cluster, while a small oscillating component is also present for the Fe8 cluster. For the first of the clusters, τ vs T (τ is the decay time of the magnetization) has a trend which, at low temperatures (T 15 K, τ follows the trend of W -1 . For the Fe8, τ follows an Arrhenius law, but with a prefactor which is smaller than the one obtained susceptibility measurements

  4. Improving estimation of kinetic parameters in dynamic force spectroscopy using cluster analysis

    Science.gov (United States)

    Yen, Chi-Fu; Sivasankar, Sanjeevi

    2018-03-01

    Dynamic Force Spectroscopy (DFS) is a widely used technique to characterize the dissociation kinetics and interaction energy landscape of receptor-ligand complexes with single-molecule resolution. In an Atomic Force Microscope (AFM)-based DFS experiment, receptor-ligand complexes, sandwiched between an AFM tip and substrate, are ruptured at different stress rates by varying the speed at which the AFM-tip and substrate are pulled away from each other. The rupture events are grouped according to their pulling speeds, and the mean force and loading rate of each group are calculated. These data are subsequently fit to established models, and energy landscape parameters such as the intrinsic off-rate (koff) and the width of the potential energy barrier (xβ) are extracted. However, due to large uncertainties in determining mean forces and loading rates of the groups, errors in the estimated koff and xβ can be substantial. Here, we demonstrate that the accuracy of fitted parameters in a DFS experiment can be dramatically improved by sorting rupture events into groups using cluster analysis instead of sorting them according to their pulling speeds. We test different clustering algorithms including Gaussian mixture, logistic regression, and K-means clustering, under conditions that closely mimic DFS experiments. Using Monte Carlo simulations, we benchmark the performance of these clustering algorithms over a wide range of koff and xβ, under different levels of thermal noise, and as a function of both the number of unbinding events and the number of pulling speeds. Our results demonstrate that cluster analysis, particularly K-means clustering, is very effective in improving the accuracy of parameter estimation, particularly when the number of unbinding events are limited and not well separated into distinct groups. Cluster analysis is easy to implement, and our performance benchmarks serve as a guide in choosing an appropriate method for DFS data analysis.

  5. Vibrational dynamics of aniline(Ar)1 and aniline(CH4)1 clusters

    Science.gov (United States)

    Nimlos, M. R.; Young, M. A.; Bernstein, E. R.; Kelley, D. F.

    1989-11-01

    The first excited electronic state (S1) vibrational dynamics of aniline(Ar)1 and aniline(CH4)1 van der Waals (vdW) clusters have been studied using molecular jet and time resolved emission spectroscopic techniques. The rates of intramolecular vibrational energy redistribution (IVR) and vibrational predissociation (VP) as functions of vibrational energy are reported for both clusters. For vibrational energy in excess of the cluster binding energy, both clusters are observed to dissociate. The dispersed emission spectra of these clusters demonstrate that aniline(Ar)1 dissociates to all energetically accessible bare molecule states and that aniline(CH4)1 dissociates selectively to only the bare molecule vibrationless state. The emission kinetics show that in the aniline(Ar)1 case, the initially excited states have nanosecond lifetimes, and intermediate cluster states have very short lifetimes. In contrast, the initially excited aniline(CH4)1 states and other intermediate vibrationally excited cluster states are very short lived (golden rule, and the density of vdW vibrational states is the most important factor in determining the relative [aniline(Ar)1 vs aniline(CH4)1] rates of IVR; (2) IVR among the vdW modes is rapid; and (3) VP rates can be calculated by a restricted vdW mode phase space Rice-Ramsberger-Kassel-Marcus theory. Since the density of vdW states is three orders of magnitude greater for aniline(CH4)1 than aniline(Ar)1 at 700 cm-1, the model predicts that IVR is slow and rate limiting in aniline(Ar)1, whereas VP is slow and rate limiting in aniline(CH4)1. The agreement of these predictions with the experimental results is very good and is discussed in detail.

  6. Dynamics in dense stellar clusters: binary black holes in galactic centres

    Science.gov (United States)

    Hemsendorf, M.

    2001-06-01

    The dynamics of a massive binary system in a galactic nucleus are presented. These are the first results from simulations applying a hybrid "self consistent field" (SCF) and direct Aarseth N-body integrator (NBODY6), which synthesises the advantages of the direct force calculation with the efficiency of the field method. The code is aimed for use on parallel architectures and is therefore applicable for collisional N-body integrations with extraordinarily large particle numbers (>105). It opens the perspective to simulate the dynamics of globular clusters with realistic collisional relaxation, as well as stellar systems surrounding a supermassive black hole in galactic nuclei.

  7. Dynamics of Dense Stellar Clusters: Binary Black Holes in Galactic Centres

    Science.gov (United States)

    Hemsendorf, M.

    The dynamics of a massive binary system in a galactic nucleus are presented. These are the first results from simulations applying a hybrid "self consistent field" (SCF) and direct Aarseth N-body integrator (NBODY6), which synthesises the advantages of the direct force calculation with the efficiency of the field method. The code is aimed for use on parallel architectures and is therefore applicable for collisional N-body integrations with extraordinarily large particle numbers (> 105). It opens the perspective to simulate the dynamics of globular clusters with realistic collisional relaxation, as well as stellar systems surrounding a supermassive black hole in galactic nuclei.

  8. Improving flow distribution in influent channels using computational fluid dynamics.

    Science.gov (United States)

    Park, No-Suk; Yoon, Sukmin; Jeong, Woochang; Lee, Seungjae

    2016-10-01

    Although the flow distribution in an influent channel where the inflow is split into each treatment process in a wastewater treatment plant greatly affects the efficiency of the process, and a weir is the typical structure for the flow distribution, to the authors' knowledge, there is a paucity of research on the flow distribution in an open channel with a weir. In this study, the influent channel of a real-scale wastewater treatment plant was used, installing a suppressed rectangular weir that has a horizontal crest to cross the full channel width. The flow distribution in the influent channel was analyzed using a validated computational fluid dynamics model to investigate (1) the comparison of single-phase and two-phase simulation, (2) the improved procedure of the prototype channel, and (3) the effect of the inflow rate on flow distribution. The results show that two-phase simulation is more reliable due to the description of the free-surface fluctuations. It should first be considered for improving flow distribution to prevent a short-circuit flow, and the difference in the kinetic energy with the inflow rate makes flow distribution trends different. The authors believe that this case study is helpful for improving flow distribution in an influent channel.

  9. Dynamics of Biofilm Regrowth in Drinking Water Distribution Systems.

    Science.gov (United States)

    Douterelo, I; Husband, S; Loza, V; Boxall, J

    2016-07-15

    The majority of biomass within water distribution systems is in the form of attached biofilm. This is known to be central to drinking water quality degradation following treatment, yet little understanding of the dynamics of these highly heterogeneous communities exists. This paper presents original information on such dynamics, with findings demonstrating patterns of material accumulation, seasonality, and influential factors. Rigorous flushing operations repeated over a 1-year period on an operational chlorinated system in the United Kingdom are presented here. Intensive monitoring and sampling were undertaken, including time-series turbidity and detailed microbial analysis using 16S rRNA Illumina MiSeq sequencing. The results show that bacterial dynamics were influenced by differences in the supplied water and by the material remaining attached to the pipe wall following flushing. Turbidity, metals, and phosphate were the main factors correlated with the distribution of bacteria in the samples. Coupled with the lack of inhibition of biofilm development due to residual chlorine, this suggests that limiting inorganic nutrients, rather than organic carbon, might be a viable component in treatment strategies to manage biofilms. The research also showed that repeat flushing exerted beneficial selective pressure, giving another reason for flushing being a viable advantageous biofilm management option. This work advances our understanding of microbiological processes in drinking water distribution systems and helps inform strategies to optimize asset performance. This research provides novel information regarding the dynamics of biofilm formation in real drinking water distribution systems made of different materials. This new knowledge on microbiological process in water supply systems can be used to optimize the performance of the distribution network and to guarantee safe and good-quality drinking water to consumers. Copyright © 2016 Douterelo et al.

  10. UAV-Assisted Dynamic Clustering of Wireless Sensor Networks for Crop Health Monitoring

    Directory of Open Access Journals (Sweden)

    Mohammad Ammad Uddin

    2018-02-01

    Full Text Available In this study, a crop health monitoring system is developed by using state of the art technologies including wireless sensors and Unmanned Aerial Vehicles (UAVs. Conventionally data is collected from sensor nodes either by fixed base stations or mobile sinks. Mobile sinks are considered a better choice nowadays due to their improved network coverage and energy utilization. Usually, the mobile sink is used in two ways: either it goes for random walk to find the scattered nodes and collect data, or follows a pre-defined path established by the ground network/clusters. Neither of these options is suitable in our scenario due to the factors like dynamic data collection, the strict targeted area required to be scanned, unavailability of a large number of nodes, dynamic path of the UAV, and most importantly, none of these are known in advance. The contribution of this paper is the formation of dynamic runtime clusters of field sensors by considering the above mentioned factors. Furthermore a mechanism (Bayesian classifier is defined to select best node as cluster head. The proposed system is validated through simulation results, lab and infield experiments using concept devices. The obtained results are encouraging, especially in terms of deployment time, energy, efficiency, throughput and ease of use.

  11. UAV-Assisted Dynamic Clustering of Wireless Sensor Networks for Crop Health Monitoring.

    Science.gov (United States)

    Uddin, Mohammad Ammad; Mansour, Ali; Jeune, Denis Le; Ayaz, Mohammad; Aggoune, El-Hadi M

    2018-02-11

    In this study, a crop health monitoring system is developed by using state of the art technologies including wireless sensors and Unmanned Aerial Vehicles (UAVs). Conventionally data is collected from sensor nodes either by fixed base stations or mobile sinks. Mobile sinks are considered a better choice nowadays due to their improved network coverage and energy utilization. Usually, the mobile sink is used in two ways: either it goes for random walk to find the scattered nodes and collect data, or follows a pre-defined path established by the ground network/clusters. Neither of these options is suitable in our scenario due to the factors like dynamic data collection, the strict targeted area required to be scanned, unavailability of a large number of nodes, dynamic path of the UAV, and most importantly, none of these are known in advance. The contribution of this paper is the formation of dynamic runtime clusters of field sensors by considering the above mentioned factors. Furthermore a mechanism (Bayesian classifier) is defined to select best node as cluster head. The proposed system is validated through simulation results, lab and infield experiments using concept devices. The obtained results are encouraging, especially in terms of deployment time, energy, efficiency, throughput and ease of use.

  12. Topology Identification of General Dynamical Network with Distributed Time Delays

    International Nuclear Information System (INIS)

    Zhao-Yan, Wu; Xin-Chu, Fu

    2009-01-01

    General dynamical networks with distributed time delays are studied. The topology of the networks are viewed as unknown parameters, which need to be identified. Some auxiliary systems (also called the network estimators) are designed to achieve this goal. Both linear feedback control and adaptive strategy are applied in designing these network estimators. Based on linear matrix inequalities and the Lyapunov function method, the sufficient condition for the achievement of topology identification is obtained. This method can also better monitor the switching topology of dynamical networks. Illustrative examples are provided to show the effectiveness of this method. (general)

  13. Dynamic Subsidy Method for Congestion Management in Distribution Networks

    DEFF Research Database (Denmark)

    Huang, Shaojun; Wu, Qiuwei

    2016-01-01

    Dynamic subsidy (DS) is a locational price paid by the distribution system operator (DSO) to its customers in order to shift energy consumption to designated hours and nodes. It is promising for demand side management and congestion management. This paper proposes a new DS method for congestion...... management in distribution networks, including the market mechanism, the mathematical formulation through a two-level optimization, and the method solving the optimization by tightening the constraints and linearization. Case studies were conducted with a one node system and the Bus 4 distribution network...... of the Roy Billinton Test System (RBTS) with high penetration of electric vehicles (EVs) and heat pumps (HPs). The case studies demonstrate the efficacy of the DS method for congestion management in distribution networks. Studies in this paper show that the DS method offers the customers a fair opportunity...

  14. An Efficient MapReduce-Based Parallel Clustering Algorithm for Distributed Traffic Subarea Division

    Directory of Open Access Journals (Sweden)

    Dawen Xia

    2015-01-01

    Full Text Available Traffic subarea division is vital for traffic system management and traffic network analysis in intelligent transportation systems (ITSs. Since existing methods may not be suitable for big traffic data processing, this paper presents a MapReduce-based Parallel Three-Phase K-Means (Par3PKM algorithm for solving traffic subarea division problem on a widely adopted Hadoop distributed computing platform. Specifically, we first modify the distance metric and initialization strategy of K-Means and then employ a MapReduce paradigm to redesign the optimized K-Means algorithm for parallel clustering of large-scale taxi trajectories. Moreover, we propose a boundary identifying method to connect the borders of clustering results for each cluster. Finally, we divide traffic subarea of Beijing based on real-world trajectory data sets generated by 12,000 taxis in a period of one month using the proposed approach. Experimental evaluation results indicate that when compared with K-Means, Par2PK-Means, and ParCLARA, Par3PKM achieves higher efficiency, more accuracy, and better scalability and can effectively divide traffic subarea with big taxi trajectory data.

  15. Clustering of comb and propolis waxes based on the distribution of aliphatic constituents

    Directory of Open Access Journals (Sweden)

    Custodio Angela R.

    2003-01-01

    Full Text Available Chemical composition data for 41 samples of propolis waxes and 9 samples of comb waxes of Apis mellifera collected mainly in Brazil were treated using Principal Component Analysis (PCA and Hierarchical Cluster Analysis (HCA. For chemometrical analysis, the distribution of hydrocarbons and residues of alcohols and carboxylic acids of monoesters were considered. The clustering obtained revealed chemical affinities and differences not previously grasped by simple eye-inspection of the data. No consistent differences were detected between comb and propolis waxes. These and previous results suggest that hydrocarbons, carboxylic acids, aliphatic alcohols and esters from both comb and propolis waxes are bee-produced compounds and, hence, the differences detected between one and another region are dependent on genetic factors related to the insects rather than the local flora. The samples analyzed were split into two main clusters, one of them comprising exclusively material collected in the State of São Paulo. The results are discussed with respect to the africanization of honeybees that first took place in that State and therefrom irradiated to other parts of Brazil.

  16. UV TO FAR-IR CATALOG OF A GALAXY SAMPLE IN NEARBY CLUSTERS: SPECTRAL ENERGY DISTRIBUTIONS AND ENVIRONMENTAL TRENDS

    International Nuclear Information System (INIS)

    Hernández-Fernández, Jonathan D.; Iglesias-Páramo, J.; Vílchez, J. M.

    2012-01-01

    In this paper, we present a sample of cluster galaxies devoted to study the environmental influence on the star formation activity. This sample of galaxies inhabits in clusters showing a rich variety in their characteristics and have been observed by the SDSS-DR6 down to M B ∼ –18, and by the Galaxy Evolution Explorer AIS throughout sky regions corresponding to several megaparsecs. We assign the broadband and emission-line fluxes from ultraviolet to far-infrared to each galaxy performing an accurate spectral energy distribution for spectral fitting analysis. The clusters follow the general X-ray luminosity versus velocity dispersion trend of L X ∝ σ 4.4 c . The analysis of the distributions of galaxy density counting up to the 5th nearest neighbor Σ 5 shows: (1) the virial regions and the cluster outskirts share a common range in the high density part of the distribution. This can be attributed to the presence of massive galaxy structures in the surroundings of virial regions. (2) The virial regions of massive clusters (σ c > 550 km s –1 ) present a Σ 5 distribution statistically distinguishable (∼96%) from the corresponding distribution of low-mass clusters (σ c –1 ). Both massive and low-mass clusters follow a similar density-radius trend, but the low-mass clusters avoid the high density extreme. We illustrate, with ABELL 1185, the environmental trends of galaxy populations. Maps of sky projected galaxy density show how low-luminosity star-forming galaxies appear distributed along more spread structures than their giant counterparts, whereas low-luminosity passive galaxies avoid the low-density environment. Giant passive and star-forming galaxies share rather similar sky regions with passive galaxies exhibiting more concentrated distributions.

  17. Electronic relaxation dynamics of a metal atom deposited on argon cluster

    International Nuclear Information System (INIS)

    Awali, Slim

    2014-01-01

    This thesis is a study on the interaction between electronically excited atomic states and a non-reactive environment. We have theoretically and experimentally studied situations where a metal atom (Ba or K) is placed in a finite size environment (argon cluster). The presence of the medium affects the electronic levels of the atom. On the other side, the excitation of the atom induces a relaxation dynamics of the electronic energy through the deformation of the cluster. The experimental part of this work focuses on two aspects: the spectroscopy and the dynamics. In both cases a first laser electronically excites the metal atom and the second ionizes the excited system. The observable is the photoelectron spectrum recorded after photoionization and possibly information on the photoion which are also produced. This pump/probe technique, with also two lasers, provide the ultrafast dynamic when the lasers pulses used are of ultrashort (60 fs). The use of nanosecond lasers leads to resonance spectroscopic measurement, unresolved temporally, which give information on the position of the energy levels of the studied system. From a theoretical point-of-view, the excited states of M-Ar n were calculated at the ab initio level, using large core pseudo-potential to limit the active electrons of the metal to valence electrons. The study of alkali metals (potassium) is especially well adapted to this method since only one electron is active. The ab-initio calculation and a Monte-Carlo simulation where coupled to optimize the geometry of the KAr n (n = 1-10) cluster when K is in the ground state of the neutral and the ion, or excited in the 4p or 5s state. Calculations were also conducted in collaboration with B. Gervais (CIMAP, Caen) on KAr n clusters having several tens of argon atoms. Absorption spectra were also calculated. From an experimental point-of-view, we were able to characterize the excited states of potassium and barium perturbed by the clusters. In both cases a

  18. Fusion – fission dynamics: fragment mass distribution studies

    Directory of Open Access Journals (Sweden)

    Bhattacharya S.

    2015-01-01

    Full Text Available Using the major accelerator facilities available in India, detailed experimental studies have been made to understand the mechanism of quasi-fission and role of nuclear shell effect in heavy nuclei. Fission fragment mass distribution has been used as the probe to explore the role of entrance channel effects on fusion-fission and quasifission dynamics. Fission fragment mass distribution has also been demonstrated to be useful to identify the phenomenon of ‘washing out’ of nuclear shell effect with excitation energy.

  19. Determination of interstellar pickup ion distributions in the solar wind with SOHO and Cluster

    Directory of Open Access Journals (Sweden)

    E. Möbius

    Full Text Available Over the last 10 years, the experimental basis for the study of the local interstellar medium has been substantially enhanced by the direct detection of interstellar pickup ions and of interstellar neutral helium within the heliosphere. Pickup ions can be studied for a wide range of interstellar species. However, currently the accuracy of the method to determine the parameters of the interstellar medium, namely neutral density, temperature and relative velocity, is hampered by two problems: (1 In most cases the crucial ionization rates are not available from simultaneous measurements and (2 the transport of the pickup ions in the interplanetary medium substantially modifies the measured spatial distribution of the ions. In this study we will discuss how the enhanced capabilities of the instrumentation on SOHO and Cluster in combination with ongoing efforts to model the pickup ion distributions will lead to a significant improvement over the coming years.

  20. Determination of interstellar pickup ion distributions in the solar wind with SOHO and Cluster

    Directory of Open Access Journals (Sweden)

    E. Möbius

    1996-05-01

    Full Text Available Over the last 10 years, the experimental basis for the study of the local interstellar medium has been substantially enhanced by the direct detection of interstellar pickup ions and of interstellar neutral helium within the heliosphere. Pickup ions can be studied for a wide range of interstellar species. However, currently the accuracy of the method to determine the parameters of the interstellar medium, namely neutral density, temperature and relative velocity, is hampered by two problems: (1 In most cases the crucial ionization rates are not available from simultaneous measurements and (2 the transport of the pickup ions in the interplanetary medium substantially modifies the measured spatial distribution of the ions. In this study we will discuss how the enhanced capabilities of the instrumentation on SOHO and Cluster in combination with ongoing efforts to model the pickup ion distributions will lead to a significant improvement over the coming years.

  1. N-Body Galaxy Dynamics Simulations on a Homogeneous Beowulf Cluster

    Science.gov (United States)

    Gipson, B.; McBride, W. R.; Kornreich, D. A.

    2004-12-01

    The galactic distribution of dark matter in disk galaxies remains an important problem in astrophysics. Modern methods in determining this distribution rely heavily on N--Body simulations. To this end we have developed a variable time step Piet Hut N--Body simulator, run using MPICH on a homogeneous 12 processor (x86) Beowulf cluster. The Hut Algorithm allows for the efficient, accurate calculation of forces between millions of points in a reasonable time. Additionally, subdividing the space into octants allows for the efficient creation O(N log (N)) of mutual nearest-neighbor data for all points. Such data are necessary for the inclusion of smoothed particle hydrodynamics (gas clouds, etc) as well as for merging the frequent, tightly bound, rapidly rotating, binary systems that decrease performance in this type of simulation. Initial tests have shown strong agreement with exhaustive O(N2) calculation results. Simulating 10,000 points yielded a total relative error of 0.32% with the exhaustive case, executing in 3.3 seconds on the cluster. General system-level tests have also been performed, including determining collapse times for cold and isothermal spherical distributions; all resulting in good agreement with analytical results. Tests on the Kuz'min galactic distribution have also resulted in expected rotational rates. We discuss the oscillatory behavior of such distributions within several constant potentials with the intention of further eliciting the distribution of dark matter within our own galaxy.

  2. Clustered, regularly interspaced short palindromic repeat (CRISPR) diversity and virulence factor distribution in avian Escherichia coli.

    Science.gov (United States)

    Fu, Qiang; Su, Zhixin; Cheng, Yuqiang; Wang, Zhaofei; Li, Shiyu; Wang, Heng'an; Sun, Jianhe; Yan, Yaxian

    In order to investigate the diverse characteristics of clustered, regularly interspaced short palindromic repeat (CRISPR) arrays and the distribution of virulence factor genes in avian Escherichia coli, 80 E. coli isolates obtained from chickens with avian pathogenic E. coli (APEC) or avian fecal commensal E. coli (AFEC) were identified. Using the multiplex polymerase chain reaction (PCR), five genes were subjected to phylogenetic typing and examined for CRISPR arrays to study genetic relatedness among the strains. The strains were further analyzed for CRISPR loci and virulence factor genes to determine a possible association between their CRISPR elements and their potential virulence. The strains were divided into five phylogenetic groups: A, B1, B2, D and E. It was confirmed that two types of CRISPR arrays, CRISPR1 and CRISPR2, which contain up to 246 distinct spacers, were amplified in most of the strains. Further classification of the isolates was achieved by sorting them into nine CRISPR clusters based on their spacer profiles, which indicates a candidate typing method for E. coli. Several significant differences in invasion-associated gene distribution were found between the APEC isolates and the AFEC isolates. Our results identified the distribution of 11 virulence genes and CRISPR diversity in 80 strains. It was demonstrated that, with the exception of iucD and aslA, there was no sharp demarcation in the gene distribution between the pathogenic (APEC) and commensal (AFEC) strains, while the total number of indicated CRISPR spacers may have a positive correlation with the potential pathogenicity of the E. coli isolates. Copyright © 2016. Published by Elsevier Masson SAS.

  3. Distribution of Zeros and the Equation of State. III : Cluster Series, the Ideal Fermi-Dirac Gas and Other Problems

    OpenAIRE

    Kazuyosi, IKEDA; Department of Applied Physics, Osaka University

    1982-01-01

    The radius of convergence of the cluster series (expressing the equation of state) is discussed in connection with the distribution of zeros of the grand partition function on the complex z (= activity) plane, by giving various examples of circular distribution. Anomalous phase transitions and phase transitions of third order are considered by showing some examples of circular distribution of zeros. For the ideal Fermi-Dirac gas, the distribution function of zeros, lying on the part of the ne...

  4. Cluster analysis of accelerated molecular dynamics simulations: A case study of the decahedron to icosahedron transition in Pt nanoparticles

    Science.gov (United States)

    Huang, Rao; Lo, Li-Ta; Wen, Yuhua; Voter, Arthur F.; Perez, Danny

    2017-10-01

    Modern molecular-dynamics-based techniques are extremely powerful to investigate the dynamical evolution of materials. With the increase in sophistication of the simulation techniques and the ubiquity of massively parallel computing platforms, atomistic simulations now generate very large amounts of data, which have to be carefully analyzed in order to reveal key features of the underlying trajectories, including the nature and characteristics of the relevant reaction pathways. We show that clustering algorithms, such as the Perron Cluster Cluster Analysis, can provide reduced representations that greatly facilitate the interpretation of complex trajectories. To illustrate this point, clustering tools are used to identify the key kinetic steps in complex accelerated molecular dynamics trajectories exhibiting shape fluctuations in Pt nanoclusters. This analysis provides an easily interpretable coarse representation of the reaction pathways in terms of a handful of clusters, in contrast to the raw trajectory that contains thousands of unique states and tens of thousands of transitions.

  5. An alternative phase-space distribution to sample initial conditions for classical dynamics simulations

    International Nuclear Information System (INIS)

    Garcia-Vela, A.

    2002-01-01

    A new quantum-type phase-space distribution is proposed in order to sample initial conditions for classical trajectory simulations. The phase-space distribution is obtained as the modulus of a quantum phase-space state of the system, defined as the direct product of the coordinate and momentum representations of the quantum initial state. The distribution is tested by sampling initial conditions which reproduce the initial state of the Ar-HCl cluster prepared by ultraviolet excitation, and by simulating the photodissociation dynamics by classical trajectories. The results are compared with those of a wave packet calculation, and with a classical simulation using an initial phase-space distribution recently suggested. A better agreement is found between the classical and the quantum predictions with the present phase-space distribution, as compared with the previous one. This improvement is attributed to the fact that the phase-space distribution propagated classically in this work resembles more closely the shape of the wave packet propagated quantum mechanically

  6. Responses of Cloud Type Distributions to the Large-Scale Dynamical Circulation: Water Budget-Related Dynamical Phase Space and Dynamical Regimes

    Science.gov (United States)

    Wong, Sun; Del Genio, Anthony; Wang, Tao; Kahn, Brian; Fetzer, Eric J.; L'Ecuyer, Tristan S.

    2015-01-01

    Goals: Water budget-related dynamical phase space; Connect large-scale dynamical conditions to atmospheric water budget (including precipitation); Connect atmospheric water budget to cloud type distributions.

  7. Optimal clustering of kinetic patterns on malignant breast lesions: comparison between K-means clustering and three-time-points method in dynamic contrast-enhanced MRI.

    Science.gov (United States)

    Lee, S H; Kim, J H; Kim, K G; Park, J S; Park, S J; Moon, W K

    2007-01-01

    Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is useful for breast cancer diagnosis and treatment planning. Nevertheless, due to the multi-temporal nature of DCE-MRI data, the assessment of early stage breast cancer is a challenging task. In this study, we applied an unsupervised clustering approach and cluster validation technique to the analysis of malignant intral-tumoral kinetic curves in DCE-MRI. K-means cluster analysis was performed from real world malignant tumor cases and the data were transformed into an optimal number of reference patterns representative each cluster. The optimal number of clusters was estimated by a cluster validation index, which was calculated with the ratio of inter-class scatter to intra-class scatter. This technique then classifies tumor specific patterns from a given MRI data by measuring the vector distances from the reference pattern set, and compared the result from the k-means clustering with that from three-time-points (3TP) method, which represents a clinical standard protocol for analysis of tumor kinetics. The evaluation of twenty five cases indicates that optimal k-means clustering reflects partitioning intra-tumoral kinetic patterns better than the 3TP technique. This method will greatly enhance the capability of radiologists to identify and characterize internal kinetic heterogeneity and vascular change of a tumor in breast DCE-MRI.

  8. Optimal Operation of Radial Distribution Systems Using Extended Dynamic Programming

    DEFF Research Database (Denmark)

    Lopez, Juan Camilo; Vergara, Pedro P.; Lyra, Christiano

    2018-01-01

    An extended dynamic programming (EDP) approach is developed to optimize the ac steady-state operation of radial electrical distribution systems (EDS). Based on the optimality principle of the recursive Hamilton-Jacobi-Bellman equations, the proposed EDP approach determines the optimal operation...... approach is illustrated using real-scale systems and comparisons with commercial programming solvers. Finally, generalizations to consider other EDS operation problems are also discussed....

  9. Team dynamics in virtual, partially distributed teams : optimal role fulfillment

    OpenAIRE

    Eubanks, Dawn L.; Palanski, Michael; Olabisi, Joy; Joinson, Adam; Dove, James

    2016-01-01

    In this study, we explored team roles in virtual, partially distributed teams, or vPDTs (teams with at least one co-located subgroup and at least two subgroups that are geographically dispersed but that collaborate virtually). Past research on virtual teams emphasizes the importance of team dynamics. We argue that the following three roles are particularly important for high functioning virtual teams: Project Coordinator, Implementer and Completer-Finisher. We hypothesized that the highest pe...

  10. SEARCHING FOR COOLING SIGNATURES IN STRONG LENSING GALAXY CLUSTERS: EVIDENCE AGAINST BARYONS SHAPING THE MATTER DISTRIBUTION IN CLUSTER CORES

    International Nuclear Information System (INIS)

    Blanchard, Peter K.; Bayliss, Matthew B.; McDonald, Michael; Dahle, Håkon; Gladders, Michael D.; Sharon, Keren; Mushotzky, Richard

    2013-01-01

    The process by which the mass density profile of certain galaxy clusters becomes centrally concentrated enough to produce high strong lensing (SL) cross-sections is not well understood. It has been suggested that the baryonic condensation of the intracluster medium (ICM) due to cooling may drag dark matter to the cores and thus steepen the profile. In this work, we search for evidence of ongoing ICM cooling in the first large, well-defined sample of SL selected galaxy clusters in the range 0.1 0.2 and shows no statistically significant deviation from the total cluster population. Specific star formation rates, as traced by the strength of the 4000 Å break, D 4000 , are also consistent with the general cluster population. Finally, we use optical imaging of the SL clusters to measure the angular separation, R arc , between the arc and the center of mass of each lensing cluster in our sample and test for evidence of changing [O II] emission and D 4000 as a function of R arc , a proxy observable for SL cross-sections. D 4000 is constant with all values of R arc , and the [O II] emission fractions show no dependence on R arc for R arc > 10'' and only very marginal evidence of increased weak [O II] emission for systems with R arc < 10''. These results argue against the ability of baryonic cooling associated with cool core activity in the cores of galaxy clusters to strongly modify the underlying dark matter potential, leading to an increase in SL cross-sections

  11. Molecular dynamics simulations of nucleation and phase transitions in molecular clusters of hexafluorides

    International Nuclear Information System (INIS)

    Xu, S.

    1993-01-01

    Molecular dynamics simulations of nucleation and phase transitions in TeF 6 and SeF 6 clusters containing 100-350 molecules were carried out. Simulations successfully reproduced the crystalline structures observed in electron diffraction studies of large clusters (containing about 10 4 molecules) of the same materials. When the clusters were cooled, they spontaneously underwent the same bcc the monoclinic phase transition in simulations as in experiment, despite the million-fold difference in the time scales involved. Other transitions observed included melting and freezing. Several new techniques based on molecular translation and orientation were introduced to identify different condensed phases, to study nucleation and phase transitions, and to define characteristic temperatures of transitions. The solid-state transition temperatures decreased with cluster size in the same way as did the melting temperature, in that the depression of transition temperature was inversely proportional to the cluster radius. Rotational melting temperatures, as inferred from the rotational diffusion of molecules, coincided with those of the solid-state transition. Nucleation in liquid-solid and bcc-monoclinic transitions started in the interior of clusters on cooling, and at the surface on heating. Transition temperatures on cooling were always lower than those on heating due to the barriers to nucleation. Linear growth rates of nuclei in freezing were an order of magnitude lower than those in the bcc-monoclinic transition. Revealing evidence about the molecular behavior associated with phase changes was found. Simulations showed the formation of the actual transition complexes along the transition pathway, i.e., the critical nuclei of the new phase. These nuclei, consisting of a few dozen molecules, were distinguishable in the midst of the surrounding matter

  12. Adaptive Marginal Costs-Based Distributed Economic Control of Microgrid Clusters Considering Line Loss

    Directory of Open Access Journals (Sweden)

    Xiaoqian Zhou

    2017-12-01

    Full Text Available When several microgrids (MG are interconnected into microgrid clusters (MGC, they have great potential to improve their reliability. Traditional droop control tends to make the total operating costs higher as the power is distributed by capacity ratios of distributed energy resources (DERs. This paper proposes an adaptive distributed economic control for islanded microgrids which considers line loss, specifically, an interesting marginal costs-based economic droop control is proposed, and consensus-based adaptive controller is applied, to deal with power limits and capacity constraints for storage. The whole expense can be effectively lowered by achieving identical marginal costs for DERs in MGC. Specially, the capacity constraints only for storages are also included to do further optimization. Moreover, consensus-based distributed secondary controllers are used to rapidly restore system frequency and voltage magnitudes. The above controllers only need to interact with neighbor DERs by a sparse communication network, eliminating the necessity of a central controller and enhancing the stability. A MGC, incorporating three microgrids, is used to verify the effectiveness of the proposed methods.

  13. Icosahedron-fcc transition size by molecular dynamics simulation of Lennard-Jones clusters at a finite temperature.

    Science.gov (United States)

    Ikeshoji, T; Torchet, G; de Feraudy, M F; Koga, K

    2001-03-01

    We studied finite-temperature ensembles of solid clusters produced by cooling liquid droplets either by evaporation or by a thermostat through a molecular dynamics calculation using the Lennard-Jones potential. The ensembles consist of either single or binary component clusters with 25% of the atoms 8% smaller in diameter than the other 75%. These clusters (380 clusters in total) exhibit various structures in the size range of n=160-2200, where n is the number of atoms in a cluster. For increasing size, the clusters show a gradual transition from icosahedral to a variety of structures: decahedral, face centered cubic, a small amount of hexagonal, and some icosahedral structures. They are asymmetrical or faulted. Electron diffraction patterns calculated with average structure factors of clusters after grouping them into several size regions are very similar to those experimentally observed. The size transition is around n=450 for single component clusters whatever the cooling process, evaporation or thermostat. This size is smaller than the experimental transition size estimated for argon clusters formed in a supersonic expansion. The transition size for binary component clusters is around n=600 for evaporative cooling, and larger for thermostatic cooling. The larger transition size found for the binary component clusters is consistent with the large icosahedral Au-Fe and Au-Cu alloy clusters observed experimentally.

  14. Gravitational and capillary soil moisture dynamics for distributed hydrologic models

    Directory of Open Access Journals (Sweden)

    A. Castillo

    2015-04-01

    Full Text Available Distributed and continuous catchment models are used to simulate water and energy balance and fluxes across varied topography and landscape. The landscape is discretized into computational plan elements at resolutions of 101–103 m, and soil moisture is the hydrologic state variable. At the local scale, the vertical soil moisture dynamics link hydrologic fluxes and provide continuity in time. In catchment models these local-scale processes are modeled using 1-D soil columns that are discretized into layers that are usually 10−3–10−1 m in thickness. This creates a mismatch between the horizontal and vertical scales. For applications across large domains and in ensemble mode, this treatment can be a limiting factor due to its high computational demand. This study compares continuous multi-year simulations of soil moisture at the local scale using (i a 1-pixel version of a distributed catchment hydrologic model and (ii a benchmark detailed soil water physics solver. The distributed model uses a single soil layer with a novel dual-pore structure and employs linear parameterization of infiltration and some other fluxes. The detailed solver uses multiple soil layers and employs nonlinear soil physics relations to model flow in unsaturated soils. Using two sites with different climates (semiarid and sub-humid, it is shown that the efficient parameterization in the distributed model captures the essential dynamics of the detailed solver.

  15. The effect of distribution of second phase on dynamic damage

    Science.gov (United States)

    Fensin, S. J.; Jones, D. R.; Walker, E. K.; Farrow, A.; Imhoff, S. D.; Clarke, K.; Trujillo, C. P.; Martinez, D. T.; Gray, G. T.; Cerreta, E. K.

    2016-08-01

    For ductile metals, dynamic fracture occurs principally through void nucleation, growth, and coalescence at heterogeneities in the microstructure. Previous experimental research on high purity metals has shown that microstructural features, such as grain boundaries, inclusions, vacancies, and heterogeneities, can act as initial void nucleation sites. In addition, other research on two-phase materials has also highlighted the importance of the properties of a second phase itself in determining the dynamic response of the overall material. However, previous research has not investigated the effects of the distribution of a second phase on damage nucleation and evolution. To approach this problem in a systematic manner, two copper alloys with 1% lead materials, with the same Pb concentration but different Pb distributions, have been investigated. A new CuPb alloy was cast with a more homogeneous distribution of Pb as compared to a CuPb where the Pb congregated in large "stringer" type configurations. These materials were shock loaded at ˜1.2 GPa and soft recovered. In-situ free surface velocity information, and post mortem metallography, reveals that even though the spall strength of both the materials were similar, the total extent and details of damage in the materials varied by 15%. This suggests that altering the distribution of Pb in the Cu matrix leads to the creation of more void nucleation sites and also changed the rate of void growth.

  16. The Gaia-ESO Survey: radial distribution of abundances in the Galactic disc from open clusters and young-field stars

    Science.gov (United States)

    Magrini, L.; Randich, S.; Kordopatis, G.; Prantzos, N.; Romano, D.; Chieffi, A.; Limongi, M.; François, P.; Pancino, E.; Friel, E.; Bragaglia, A.; Tautvaišienė, G.; Spina, L.; Overbeek, J.; Cantat-Gaudin, T.; Donati, P.; Vallenari, A.; Sordo, R.; Jiménez-Esteban, F. M.; Tang, B.; Drazdauskas, A.; Sousa, S.; Duffau, S.; Jofré, P.; Gilmore, G.; Feltzing, S.; Alfaro, E.; Bensby, T.; Flaccomio, E.; Koposov, S.; Lanzafame, A.; Smiljanic, R.; Bayo, A.; Carraro, G.; Casey, A. R.; Costado, M. T.; Damiani, F.; Franciosini, E.; Hourihane, A.; Lardo, C.; Lewis, J.; Monaco, L.; Morbidelli, L.; Sacco, G.; Sbordone, L.; Worley, C. C.; Zaggia, S.

    2017-06-01

    Context. The spatial distribution of elemental abundances in the disc of our Galaxy gives insights both on its assembly process and subsequent evolution, and on the stellar nucleogenesis of the different elements. Gradients can be traced using several types of objects as, for instance, (young and old) stars, open clusters, HII regions, planetary nebulae. Aims: We aim to trace the radial distributions of abundances of elements produced through different nucleosynthetic channels - the α-elements O, Mg, Si, Ca and Ti, and the iron-peak elements Fe, Cr, Ni and Sc - by use of the Gaia-ESO IDR4 results for open clusters and young-field stars. Methods: From the UVES spectra of member stars, we have determined the average composition of clusters with ages > 0.1 Gyr. We derived statistical ages and distances of field stars. We traced the abundance gradients using the cluster and field populations and compared them with a chemo-dynamical Galactic evolutionary model. Results: The adopted chemo-dynamical model, with the new generation of metallicity-dependent stellar yields for massive stars, is able to reproduce the observed spatial distributions of abundance ratios, in particular the abundance ratios of [O/Fe] and [Mg/Fe] in the inner disc (5 kpc Tables A.1-A.4 are also available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/603/A2

  17. Distributed interactive graphics applications in computational fluid dynamics

    International Nuclear Information System (INIS)

    Rogers, S.E.; Buning, P.G.; Merritt, F.J.

    1987-01-01

    Implementation of two distributed graphics programs used in computational fluid dynamics is discussed. Both programs are interactive in nature. They run on a CRAY-2 supercomputer and use a Silicon Graphics Iris workstation as the front-end machine. The hardware and supporting software are from the Numerical Aerodynamic Simulation project. The supercomputer does all numerically intensive work and the workstation, as the front-end machine, allows the user to perform real-time interactive transformations on the displayed data. The first program was written as a distributed program that computes particle traces for fluid flow solutions existing on the supercomputer. The second is an older post-processing and plotting program modified to run in a distributed mode. Both programs have realized a large increase in speed over that obtained using a single machine. By using these programs, one can learn quickly about complex features of a three-dimensional flow field. Some color results are presented

  18. Automatic segmentation of dynamic neuroreceptor single-photon emission tomography images using fuzzy clustering

    International Nuclear Information System (INIS)

    Acton, P.D.; Pilowsky, L.S.; Kung, H.F.; Ell, P.J.

    1999-01-01

    The segmentation of medical images is one of the most important steps in the analysis and quantification of imaging data. However, partial volume artefacts make accurate tissue boundary definition difficult, particularly for images with lower resolution commonly used in nuclear medicine. In single-photon emission tomography (SPET) neuroreceptor studies, areas of specific binding are usually delineated by manually drawing regions of interest (ROIs), a time-consuming and subjective process. This paper applies the technique of fuzzy c-means clustering (FCM) to automatically segment dynamic neuroreceptor SPET images. Fuzzy clustering was tested using a realistic, computer-generated, dynamic SPET phantom derived from segmenting an MR image of an anthropomorphic brain phantom. Also, the utility of applying FCM to real clinical data was assessed by comparison against conventional ROI analysis of iodine-123 iodobenzamide (IBZM) binding to dopamine D 2 /D 3 receptors in the brains of humans. In addition, a further test of the methodology was assessed by applying FCM segmentation to [ 123 I]IDAM images (5-iodo-2-[[2-2-[(dimethylamino)methyl]phenyl]thio] benzyl alcohol) of serotonin transporters in non-human primates. In the simulated dynamic SPET phantom, over a wide range of counts and ratios of specific binding to background, FCM correlated very strongly with the true counts (correlation coefficient r 2 >0.99, P 123 I]IBZM data comparable with manual ROI analysis, with the binding ratios derived from both methods significantly correlated (r 2 =0.83, P<0.0001). Fuzzy clustering is a powerful tool for the automatic, unsupervised segmentation of dynamic neuroreceptor SPET images. Where other automated techniques fail completely, and manual ROI definition would be highly subjective, FCM is capable of segmenting noisy images in a robust and repeatable manner. (orig.)

  19. Exploring the expansion dynamics of the universe from galaxy cluster surveys

    Science.gov (United States)

    Wang, Deng; Meng, Xin-He

    2017-12-01

    To understand the expansion dynamics of the universe from galaxy cluster scales, using the angular diameter distance (ADD) data from two different galaxy cluster surveys, we constrain four cosmological models to explore the underlying value of H0 and employ the model-independent Gaussian Processes to investigate the evolution of the equation of state of dark energy. The ADD data in the X-ray bands consists of two samples covering the redshift ranges [0.023, 0.784] and [0.14, 0.89], respectively. We find that: (i) For these two samples, the obtained values of H0 are more consistent with the recent local observation by Riess et al. than the global measurement by the Planck Collaboration, and the ΛCDM model is still preferred utilizing the information criterions; (ii) For the first sample, there is no evidence of dynamical dark energy (DDE) at the 2 σ confidence level (CL); (iii) For the second one, the reconstructed equation of state of dark energy exhibits a phantom-crossing behavior in the relatively low redshift range over the 2 σ CL, which gives a hint that the late-time universe may be actually dominated by the DDE from galaxy cluster scales; (iv) By adding a combination of Type Ia Supernovae, cosmic chronometers and Planck-2015 shift parameter and HII galaxy measurements into both ADD samples, the DDE exists evidently over the 2 σ CL.

  20. On helium cluster dynamics in tungsten plasma facing components of fusion devices

    International Nuclear Information System (INIS)

    Krasheninnikov, S.I.; Faney, T.; Wirth, B.D.

    2014-01-01

    This paper describes the dynamics of helium clustering behaviour within either a nanometer-sized tendril of fuzz, or a half-space domain, as predicted by a reaction–diffusion model. This analysis has identified a dimensionless parameter, P Δ , which is a balance of the reaction and diffusion actions of insoluble He in a metal matrix and which governs the self-trapping effects of He into growing bubbles within a tendril. The impact of He self-trapping, as well as trapping caused by pre-existing traps in the form of lattice defects or clusters of impurities, within a half-space domain results in the formation of a densely packed layer of nanometer-sized bubbles with high number density. This prediction is consistent with available experimental observations in which a dense zone of helium bubbles is observed in tungsten, which are compared to estimates of the layer characteristics. Direct numerical simulation of the reaction–diffusion cluster dynamics supports the analysis presented here. (paper)

  1. Real-time dynamics of RNA Polymerase II clustering in live human cells

    Science.gov (United States)

    Cisse, Ibrahim

    2014-03-01

    Transcription is the first step in the central dogma of molecular biology, when genetic information encoded on DNA is made into messenger RNA. How this fundamental process occurs within living cells (in vivo) is poorly understood,[1] despite extensive biochemical characterizations with isolated biomolecules (in vitro). For high-order organisms, like humans, transcription is reported to be spatially compartmentalized in nuclear foci consisting of clusters of RNA Polymerase II, the enzyme responsible for synthesizing all messenger RNAs. However, little is known of when these foci assemble or their relative stability. We developed an approach based on photo-activation localization microscopy (PALM) combined with a temporal correlation analysis, which we refer to as tcPALM. The tcPALM method enables the real-time characterization of biomolecular spatiotemporal organization, with single-molecule sensitivity, directly in living cells.[2] Using tcPALM, we observed that RNA Polymerase II clusters form transiently, with an average lifetime of 5.1 (+/- 0.4) seconds. Stimuli affecting transcription regulation yielded orders of magnitude changes in the dynamics of the polymerase clusters, implying that clustering is regulated and plays a role in the cells ability to effect rapid response to external signals. Our results suggest that the transient crowding of enzymes may aid in rate-limiting steps of genome regulation.

  2. VR-Cluster: Dynamic Migration for Resource Fragmentation Problem in Virtual Router Platform

    Directory of Open Access Journals (Sweden)

    Xianming Gao

    2016-01-01

    Full Text Available Network virtualization technology is regarded as one of gradual schemes to network architecture evolution. With the development of network functions virtualization, operators make lots of effort to achieve router virtualization by using general servers. In order to ensure high performance, virtual router platform usually adopts a cluster of general servers, which can be also regarded as a special cloud computing environment. However, due to frequent creation and deletion of router instances, it may generate lots of resource fragmentation to prevent platform from establishing new router instances. In order to solve “resource fragmentation problem,” we firstly propose VR-Cluster, which introduces two extra function planes including switching plane and resource management plane. Switching plane is mainly used to support seamless migration of router instances without packet loss; resource management plane can dynamically move router instances from one server to another server by using VR-mapping algorithms. Besides, three VR-mapping algorithms including first-fit mapping algorithm, best-fit mapping algorithm, and worst-fit mapping algorithm are proposed based on VR-Cluster. At last, we establish VR-Cluster protosystem by using general X86 servers, evaluate its migration time, and further analyze advantages and disadvantages of our proposed VR-mapping algorithms to solve resource fragmentation problem.

  3. Cluster formation restricts dynamic nuclear polarization of xenon in solid mixtures.

    Science.gov (United States)

    Kuzma, N N; Pourfathi, M; Kara, H; Manasseh, P; Ghosh, R K; Ardenkjaer-Larsen, J H; Kadlecek, S J; Rizi, R R

    2012-09-14

    During dynamic nuclear polarization (DNP) at 1.5 K and 5 T, (129)Xe nuclear magnetic resonance (NMR) spectra of a homogeneous xenon/1-propanol/trityl-radical solid mixture exhibit a single peak, broadened by (1)H neighbors. A second peak appears upon annealing for several hours at 125 K. Its characteristic width and chemical shift indicate the presence of spontaneously formed pure Xe clusters. Microwave irradiation at the appropriate frequencies can bring both peaks to either positive or negative polarization. The peculiar time evolution of (129)Xe polarization in pure Xe clusters during DNP can be modelled as an interplay of spin diffusion and T(1) relaxation. Our simple spherical-cluster model offers a sensitive tool to evaluate major DNP parameters in situ, revealing a severe spin-diffusion bottleneck at the cluster boundaries and a significant sample overheating due to microwave irradiation. Subsequent DNP system modifications designed to reduce the overheating resulted in four-fold increase of (129)Xe polarization, from 5.3% to 21%.

  4. Energetics and dynamics of the neutralization of clustered ions in ammonia and water vapour

    International Nuclear Information System (INIS)

    Sennhauser, E.S.; Armstrong, D.A.

    1978-01-01

    The energetics and dynamics of neutralization reactions of clustered ions in ammonia and water vapour have been analysed. Neutralization rate coefficients were calculated for the ions in ammonia and for H + .(H 2 O)sub(n) combining with various clustered anions in water vapour up to densities of 4 x 10 19 molecule cm -3 at 390 K. In the case of ammonia, calculations were also performed at 298 K. For all systems, fractional contributions of the neutralization coefficients for specific cluster sizes to the overall coefficient αsub(eff) were evaluated. The computed value of αsub(eff) for NH 3 was in reasonable agreement with experimental data in the [NH 3 ] range 0.3 to 4 x 10 19 molecule cm -3 , and general trends stemming from the effects of increasing ion mass were pointed out. Calculations of energies of individual cluster sizes indicate possible neutralization reaction mechanisms. With some exception, proton transfer is the only possible path and no H atoms should be formed. This is in general agreement with literature results for water vapour at approximately 390 K and with [H 2 O] >= 2 x 10 x 10 19 molecule cm -3 . (author)

  5. Nanoplasma dynamics of single large xenon clusters irradiated with superintense x-ray pulses from the linac coherent light source free-electron laser.

    Science.gov (United States)

    Gorkhover, T; Adolph, M; Rupp, D; Schorb, S; Epp, S W; Erk, B; Foucar, L; Hartmann, R; Kimmel, N; Kühnel, K-U; Rolles, D; Rudek, B; Rudenko, A; Andritschke, R; Aquila, A; Bozek, J D; Coppola, N; Erke, T; Filsinger, F; Gorke, H; Graafsma, H; Gumprecht, L; Hauser, G; Herrmann, S; Hirsemann, H; Hömke, A; Holl, P; Kaiser, C; Krasniqi, F; Meyer, J-H; Matysek, M; Messerschmidt, M; Miessner, D; Nilsson, B; Pietschner, D; Potdevin, G; Reich, C; Schaller, G; Schmidt, C; Schopper, F; Schröter, C D; Schulz, J; Soltau, H; Weidenspointner, G; Schlichting, I; Strüder, L; Ullrich, J; Möller, T; Bostedt, C

    2012-06-15

    The plasma dynamics of single mesoscopic Xe particles irradiated with intense femtosecond x-ray pulses exceeding 10(16)  W/cm2 from the Linac Coherent Light Source free-electron laser are investigated. Simultaneous recording of diffraction patterns and ion spectra allows eliminating the influence of the laser focal volume intensity and particle size distribution. The data show that for clusters illuminated with intense x-ray pulses, highly charged ionization fragments in a narrow distribution are created and that the nanoplasma recombination is efficiently suppressed.

  6. Distributed Energy Resources and Dynamic Microgrid: An Integrated Assessment

    Science.gov (United States)

    Shang, Duo Rick

    The overall goal of this thesis is to improve understanding in terms of the benefit of DERs to both utility and to electricity end-users when integrated in power distribution system. To achieve this goal, a series of two studies was conducted to assess the value of DERs when integrated with new power paradigms. First, the arbitrage value of DERs was examined in markets with time-variant electricity pricing rates (e.g., time of use, real time pricing) under a smart grid distribution paradigm. This study uses a stochastic optimization model to estimate the potential profit from electricity price arbitrage over a five-year period. The optimization process involves two types of PHEVs (PHEV-10, and PHEV-40) under three scenarios with different assumptions on technology performance, electricity market and PHEV owner types. The simulation results indicate that expected arbitrage profit is not a viable option to engage PHEVs in dispatching and in providing ancillary services without more favorable policy and PHEV battery technologies. Subsidy or change in electricity tariff or both are needed. Second, it examined the concept of dynamic microgrid as a measure to improve distribution resilience, and estimates the prices of this emerging service. An economic load dispatch (ELD) model is developed to estimate the market-clearing price in a hypothetical community with single bid auction electricity market. The results show that the electricity market clearing price on the dynamic microgrid is predominantly decided by power output and cost of electricity of each type of DGs. At circumstances where CHP is the only source, the electricity market clearing price in the island is even cheaper than the on-grid electricity price at normal times. Integration of PHEVs in the dynamic microgrid will increase electricity market clearing prices. It demonstrates that dynamic microgrid is an economically viable alternative to enhance grid resilience.

  7. World energy intensity convergence revisited: A weighted distribution dynamics approach

    International Nuclear Information System (INIS)

    Herrerias, M.J.

    2012-01-01

    The aim of this paper is to investigate the process of convergence as regards energy intensity in the case of large group countries over the period 1971–2008. In doing so, we focus on the distribution dynamics approach. The first novel aspect of this study consists in the fact that it analyses whether the convergence patterns differ when the population is taken into account, while the second one consists in investigating the convergence process in the case of total energy intensity, fossil fuel and alternative and nuclear intensity for the overall sample of countries as well as differentiating between develop and developing countries. On the one hand, our results indicate that the convergence patterns do differ once we weight the transition matrix by population, since we find more evidence against divergence. Moreover, a significant persistence is also found in the intra-distribution dynamics, which in turn influences the speed at which the steady state is achieved. On the other hand, the Kernel density estimates and the stationary distribution show that the distribution becomes at least bimodal in the former and clearly multimodal in the latter, thereby implying that convergence occurs within a group of countries. This phenomenon is present in all sources of energy examined, but in the case of alternative and nuclear intensity there are more symptoms of convergence. Developing countries converge at higher energy intensity ratios, while in the case of developed countries there are at least two convergence clubs, one in the lowest levels of energy intensity and another with higher levels of energy intensity. These results show the need to promote further energy-saving measures in the sample of countries examined. - Highlights: ► Energy intensity convergence is analysed in the case of 83 countries. ► We use the dynamic of the distribution approach. ► We weight the distribution by population of each country. ► Results indicate that weighting by population

  8. Statistical analysis of rockfall volume distributions: Implications for rockfall dynamics

    Science.gov (United States)

    Dussauge, Carine; Grasso, Jean-Robert; Helmstetter, AgnèS.

    2003-06-01

    We analyze the volume distribution of natural rockfalls on different geological settings (i.e., calcareous cliffs in the French Alps, Grenoble area, and granite Yosemite cliffs, California Sierra) and different volume ranges (i.e., regional and worldwide catalogs). Contrary to previous studies that included several types of landslides, we restrict our analysis to rockfall sources which originated on subvertical cliffs. For the three data sets, we find that the rockfall volumes follow a power law distribution with a similar exponent value, within error bars. This power law distribution was also proposed for rockfall volumes that occurred along road cuts. All these results argue for a recurrent power law distribution of rockfall volumes on subvertical cliffs, for a large range of rockfall sizes (102-1010 m3), regardless of the geological settings and of the preexisting geometry of fracture patterns that are drastically different on the three studied areas. The power law distribution for rockfall volumes could emerge from two types of processes. First, the observed power law distribution of rockfall volumes is similar to the one reported for both fragmentation experiments and fragmentation models. This argues for the geometry of rock mass fragment sizes to possibly control the rockfall volumes. This way neither cascade nor avalanche processes would influence the rockfall volume distribution. Second, without any requirement of scale-invariant quenched heterogeneity patterns, the rock mass dynamics can arise from avalanche processes driven by fluctuations of the rock mass properties, e.g., cohesion or friction angle. This model may also explain the power law distribution reported for landslides involving unconsolidated materials. We find that the exponent values of rockfall volume on subvertical cliffs, 0.5 ± 0.2, is significantly smaller than the 1.2 ± 0.3 value reported for mixed landslide types. This change of exponents can be driven by the material strength, which

  9. Dynamics of the intermediate-age elliptical LMC cluster NGC 1978

    Science.gov (United States)

    Fischer, Philippe; Welch, Douglas L.; Mateo, Mario

    1992-01-01

    BV CCD images and echelle spectra of 35 giants are used to examine the internal dynamics of the elliptical LMC cluster NGC 1978. Projected radii for the giants range from 1.4 to 20.0, and the mean estimated stellar velocity uncertainty is 1.6 km/s; the mean cluster velocity is 293.3 +/-1.0 km/s. BV profiles were constructed to projected radii of greater than 100 pc. The single-mass models provided better agreement with the surface photometry. Among multimass models, there is slightly better agreement seen for the models with shallow mass functions. The nonrotating model was found to be in better agreement with the kinematic data, although the rotating models could not be completely ruled out. No morphological evidence for a merger was found.

  10. Clustering, advection, and patterns in a model of population dynamics with neighborhood-dependent rates

    Science.gov (United States)

    Hernández-García, Emilio; López, Cristóbal

    2004-07-01

    We introduce a simple model of population dynamics which considers reproducing individuals or particles with birth and death rates depending on the number of other individuals in their neighborhood. The model shows an inhomogeneous quasistationary pattern with many different clusters of particles arranged periodically in space. We derive the equation for the macroscopic density of particles, perform a linear stability analysis on it, and show that there is a finite-wavelength instability leading to pattern formation. This is responsible for the approximate periodicity with which the clusters of particles arrange in the microscopic model. In addition, we consider the population when immersed in a fluid medium and analyze the influence of advection on global properties of the model, such as the average number of individuals.

  11. Dynamic connectivity algorithms for Monte Carlo simulations of the random-cluster model

    Science.gov (United States)

    Metin Elçi, Eren; Weigel, Martin

    2014-05-01

    We review Sweeny's algorithm for Monte Carlo simulations of the random cluster model. Straightforward implementations suffer from the problem of computational critical slowing down, where the computational effort per edge operation scales with a power of the system size. By using a tailored dynamic connectivity algorithm we are able to perform all operations with a poly-logarithmic computational effort. This approach is shown to be efficient in keeping online connectivity information and is of use for a number of applications also beyond cluster-update simulations, for instance in monitoring droplet shape transitions. As the handling of the relevant data structures is non-trivial, we provide a Python module with a full implementation for future reference.

  12. Dynamic connectivity algorithms for Monte Carlo simulations of the random-cluster model

    International Nuclear Information System (INIS)

    Elçi, Eren Metin; Weigel, Martin

    2014-01-01

    We review Sweeny's algorithm for Monte Carlo simulations of the random cluster model. Straightforward implementations suffer from the problem of computational critical slowing down, where the computational effort per edge operation scales with a power of the system size. By using a tailored dynamic connectivity algorithm we are able to perform all operations with a poly-logarithmic computational effort. This approach is shown to be efficient in keeping online connectivity information and is of use for a number of applications also beyond cluster-update simulations, for instance in monitoring droplet shape transitions. As the handling of the relevant data structures is non-trivial, we provide a Python module with a full implementation for future reference.

  13. Resistivity recovery simulations of electron-irradiated iron: Kinetic Monte Carlo versus cluster dynamics

    International Nuclear Information System (INIS)

    Dalla Torre, J.; Fu, C.-C.; Willaime, F.; Barbu, A.; Bocquet, J.-L.

    2006-01-01

    The isochronal resistivity recovery in high purity α-iron irradiated by electrons was successfully reproduced by a multiscale modelling approach. The stability and mobility of small self-defect clusters determined by ab initio methods were used as input data for an event based Kinetic Monte Carlo (KMC) model, used to explore the defect population evolution during the annealing and to extract the resistivity recovery peaks. In this paper, we investigate the possibility of using an efficient mesoscale model, the Cluster Dynamics (CD), instead of KMC in this approach. The comparison between the two methods for various CD initial conditions shows the importance of spatial correlations between defects, which are neglected in the CD model. However, using appropriate initial conditions, e.g. starting from the concentration of Frenkel pairs after the uncorrelated stage I E , the CD model captures the main characteristics of subsequent defect population evolution, and it can therefore be used for fast and semi-quantitative investigations

  14. Vibrational dynamics of aniline (N2)1 clusters in their first excited singlet state

    Science.gov (United States)

    Hineman, M. F.; Kim, S. K.; Bernstein, E. R.; Kelley, D. F.

    1992-04-01

    The first excited singlet state S1 vibrational dynamics of aniline(N2)1 clusters are studied and compared to previous results on aniline(CH4)1 and aniline(Ar)1. Intramolecular vibrational energy redistribution (IVR) and vibrational predissociation (VP) rates fall between the two extremes of the CH4 (fast IVR, slow VP) and Ar (slow IVR, fast VP) cluster results as is predicted by a serial IVR/VP model using Fermi's golden rule to describe IVR processes and a restricted Rice-Ramsperger-Kassel-Marcus (RRKM) theory to describe unimolecular VP rates. The density of states is the most important factor determining the rates. Two product states, 00 and 10b1, of bare aniline and one intermediate state ˜(00) in the overall IVR/VP process are observed and time resolved measurements are obtained for the 000 and ˜(000) transitions. The results are modeled with the serial mechanism described above.

  15. Molecular dynamics study of B18H22 cluster implantation into silicon

    International Nuclear Information System (INIS)

    Marques, Luis A.; Pelaz, Lourdes; Santos, Ivan

    2007-01-01

    We have carried out molecular dynamics simulations of monatomic B and octadecaborane cluster implantations into Si in order to make a comparative study and determine the advantages and drawbacks of each approach when used to fabricate shallow junctions. We have simulated a total of 1000 cascades of monatomic boron and an equivalent of 56 cascades of octadecaborane in order to have good statistics. We have obtained and analyzed the doping profiles and the amount and morphology of the damage produced within the target. Our simulation results indicate that the use of octadecaborane clusters for the implantation process shows several advantages with respect to monatomic B beams, mainly related to the reduction of channeling and the lower amount of residual damage at the end of range

  16. High dynamics of rDNA cluster location in kissing bug holocentric chromosomes (Triatominae, Heteroptera).

    Science.gov (United States)

    Panzera, Y; Pita, S; Ferreiro, M J; Ferrandis, I; Lages, C; Pérez, R; Silva, A E; Guerra, M; Panzera, F

    2012-01-01

    In this paper, we determine by fluorescent in situ hybridization the variability in the chromosomal location of 45S rDNA clusters in 38 species belonging to 7 genera of the Triatominae subfamily, using a triatomine-specific 18S rDNA probe. Our results show a striking variability at the inter- and intraspecific level, never reported so far in holocentric chromosomes, revealing the extraordinary genomic dynamics that occurred during the evolution in this group of insects. Our results also demonstrate that the chromosomal position of rDNA clusters is an important marker to disclose chromosomal differentiation in species karyotypically homogenous in their chromosome number. Copyright © 2012 S. Karger AG, Basel.

  17. Worldwide Phylogenetic Distributions and Population Dynamics of the Genus Histoplasma.

    Science.gov (United States)

    Teixeira, Marcus de M; Patané, José S L; Taylor, Maria L; Gómez, Beatriz L; Theodoro, Raquel C; de Hoog, Sybren; Engelthaler, David M; Zancopé-Oliveira, Rosely M; Felipe, Maria S S; Barker, Bridget M

    2016-06-01

    Histoplasma capsulatum comprises a worldwide complex of saprobiotic fungi mainly found in nitrogen/phosphate (often bird guano) enriched soils. The microconidia of Histoplasma species may be inhaled by mammalian hosts, and is followed by a rapid conversion to yeast that can persist in host tissues causing histoplasmosis, a deep pulmonary/systemic mycosis. Histoplasma capsulatum sensu lato is a complex of at least eight clades geographically distributed as follows: Australia, Netherlands, Eurasia, North American classes 1 and 2 (NAm 1 and NAm 2), Latin American groups A and B (LAm A and LAm B) and Africa. With the exception of the Eurasian cluster, those clades are considered phylogenetic species. Increased Histoplasma sampling (n = 234) resulted in the revision of the phylogenetic distribution and population structure using 1,563 aligned nucleotides from four protein-coding regions. The LAm B clade appears to be divided into at least two highly supported clades, which are geographically restricted to either Colombia/Argentina or Brazil respectively. Moreover, a complex population genetic structure was identified within LAm A clade supporting multiple monophylogenetic species, which could be driven by rapid host or environmental adaptation (~0.5 MYA). We found two divergent clades, which include Latin American isolates (newly named as LAm A1 and LAm A2), harboring a cryptic cluster in association with bats. At least six new phylogenetic species are proposed in the Histoplasma species complex supported by different phylogenetic and population genetics methods, comprising LAm A1, LAm A2, LAm B1, LAm B2, RJ and BAC-1 phylogenetic species. The genetic isolation of Histoplasma could be a result of differential dispersion potential of naturally infected bats and other mammals. In addition, the present study guides isolate selection for future population genomics and genome wide association studies in this important pathogen complex.

  18. Worldwide Phylogenetic Distributions and Population Dynamics of the Genus Histoplasma

    Science.gov (United States)

    Taylor, Maria L.; Gómez, Beatriz L.; Theodoro, Raquel C.; de Hoog, Sybren; Engelthaler, David M.; Zancopé-Oliveira, Rosely M.; Felipe, Maria S. S.

    2016-01-01

    Background Histoplasma capsulatum comprises a worldwide complex of saprobiotic fungi mainly found in nitrogen/phosphate (often bird guano) enriched soils. The microconidia of Histoplasma species may be inhaled by mammalian hosts, and is followed by a rapid conversion to yeast that can persist in host tissues causing histoplasmosis, a deep pulmonary/systemic mycosis. Histoplasma capsulatum sensu lato is a complex of at least eight clades geographically distributed as follows: Australia, Netherlands, Eurasia, North American classes 1 and 2 (NAm 1 and NAm 2), Latin American groups A and B (LAm A and LAm B) and Africa. With the exception of the Eurasian cluster, those clades are considered phylogenetic species. Methodology/Principal Findings Increased Histoplasma sampling (n = 234) resulted in the revision of the phylogenetic distribution and population structure using 1,563 aligned nucleotides from four protein-coding regions. The LAm B clade appears to be divided into at least two highly supported clades, which are geographically restricted to either Colombia/Argentina or Brazil respectively. Moreover, a complex population genetic structure was identified within LAm A clade supporting multiple monophylogenetic species, which could be driven by rapid host or environmental adaptation (~0.5 MYA). We found two divergent clades, which include Latin American isolates (newly named as LAm A1 and LAm A2), harboring a cryptic cluster in association with bats. Conclusions/Significance At least six new phylogenetic species are proposed in the Histoplasma species complex supported by different phylogenetic and population genetics methods, comprising LAm A1, LAm A2, LAm B1, LAm B2, RJ and BAC-1 phylogenetic species. The genetic isolation of Histoplasma could be a result of differential dispersion potential of naturally infected bats and other mammals. In addition, the present study guides isolate selection for future population genomics and genome wide association studies in this

  19. Evolution of rotating star clusters at the inelastic-collision stage. II. Dynamics of a disk of gas and stars

    International Nuclear Information System (INIS)

    Romanova, M.M.

    1985-01-01

    The dynamics of a gas--star disk embedded in a dense, mildly oblate (flattening epsilon-c or approx. =0.2--0.3 the stable disk will survive for at least half the cluster evolution time. The possibility of a thin disk of stars existing inside a dense star cluster is considered. For small epsilon-c and for disk member stars having > or approx. =0.04 the mass of the cluster members, collisions between cluster and disk stars will have no effect on the disk evolution prior to instability

  20. Molecular dynamics simulations of the interaction between 60 deg. dislocation and self-interstitial cluster in silicon

    International Nuclear Information System (INIS)

    Jing Yuhang; Meng Qingyuan; Zhao Wei

    2009-01-01

    Molecular dynamics simulations are performed to investigate the interaction between 60 deg. shuffle dislocation and tetrainterstitial (I 4 ) cluster in silicon, using Stillinger-Weber (SW) potential to calculate the interatomic forces. Based on Parrinello-Rahman method, shear stress is exerted on the model to move the dislocation. Simulation results show that the I 4 cluster can bend the dislocation line and delay the dislocation movement. During the course of intersection the dislocation line sections relatively far away from the I 4 cluster accelerate first, and then decelerate. The critical shear stress unpinning the 60 deg. dislocation from the I 4 cluster decreases as the temperature increases in the models.

  1. Privacy-Preserving k-Means Clustering under Multiowner Setting in Distributed Cloud Environments

    Directory of Open Access Journals (Sweden)

    Hong Rong

    2017-01-01

    Full Text Available With the advent of big data era, clients who lack computational and storage resources tend to outsource data mining tasks to cloud service providers in order to improve efficiency and reduce costs. It is also increasingly common for clients to perform collaborative mining to maximize profits. However, due to the rise of privacy leakage issues, the data contributed by clients should be encrypted using their own keys. This paper focuses on privacy-preserving k-means clustering over the joint datasets encrypted under multiple keys. Unfortunately, existing outsourcing k-means protocols are impractical because not only are they restricted to a single key setting, but also they are inefficient and nonscalable for distributed cloud computing. To address these issues, we propose a set of privacy-preserving building blocks and outsourced k-means clustering protocol under Spark framework. Theoretical analysis shows that our scheme protects the confidentiality of the joint database and mining results, as well as access patterns under the standard semihonest model with relatively small computational overhead. Experimental evaluations on real datasets also demonstrate its efficiency improvements compared with existing approaches.

  2. Island-size distributions in submonolayer epitaxial growth: Influence of the mobility of small clusters

    International Nuclear Information System (INIS)

    Bartelt, M.C.; Guenther, S.; Kopatzki, E.; Behm, R.J.; Evans, J.W.

    1996-01-01

    We examine the influence of dimer mobility on the size distribution of two-dimensional islands formed by irreversible nucleation and growth during deposition. We first characterize the transition in scaling of the mean island density with increasing dimer mobility, from the classic form described by Venables [Philos. Mag. 27, 697 (1973)] to the modified form for open-quote open-quote rapid close-quote close-quote mobility described by Villain et al. [J. Phys. (France) I 2, 2107 (1992)]. The corresponding transition in the asymptotic scaling function describing the shape of the island-size distribution is then also characterized. In addition, we contrast the mean-field form of the scaling function for rapid dimer mobility with that for zero mobility. Analysis of experimental data for Au/Au(100), Fe/Fe(100), Cu/Cu(100), and Pt/Pt(111) homoepitaxy reveals no clear evidence for a regime of modified island density scaling due to rapid dimer mobility. However, for Fe/Fe(100) below 400 K, we argue that mobility of small clusters significantly influences the shape of the island-size distribution, even before it affects the mean island density. copyright 1996 The American Physical Society

  3. Dynamic Root Distribution in the Community Land Model

    Science.gov (United States)

    Drewniak, B. A.

    2015-12-01

    Roots are responsible for water and nutrient uptake for plant needs, functioning to couple the above and belowground ecosystems as a photosynthesis driver. Roots respond to their environment with foraging strategies to maximize nutrient acquisition. However, roots have one of the simplest representations in Earth System Models (ESMs). Most root algorithms in ESMs consist of a fixed rooting depth and distribution, which varies only with plant functional type (PFT). Although this method works in general for many ecosystems, there are several regions (e.g., arid, boreal) where root distribution is either overestimated or underestimated resulting in plant stress induced lost productivity. In order to allow ecosystems to respond to changes in environment such as from climate change, roots require a time varying structure to adapt to heterogeneity of water and nitrogen in the soil. This work presents a new approach to representing roots in the Community Land Model. The methodology is designed to optimize root distribution for both water and nitrogen uptake, with a priority given to plant water needs. The roots can respond to the soil vertical profile of nutrients, influencing the plant extractable resources and therefore the above ground vegetation dynamics. The dynamic root profile results in an increase in gross primary productivity and crop yield.

  4. A Process for Comparing Dynamics of Distributed Space Systems Simulations

    Science.gov (United States)

    Cures, Edwin Z.; Jackson, Albert A.; Morris, Jeffery C.

    2009-01-01

    The paper describes a process that was developed for comparing the primary orbital dynamics behavior between space systems distributed simulations. This process is used to characterize and understand the fundamental fidelities and compatibilities of the modeling of orbital dynamics between spacecraft simulations. This is required for high-latency distributed simulations such as NASA s Integrated Mission Simulation and must be understood when reporting results from simulation executions. This paper presents 10 principal comparison tests along with their rationale and examples of the results. The Integrated Mission Simulation (IMSim) (formerly know as the Distributed Space Exploration Simulation (DSES)) is a NASA research and development project focusing on the technologies and processes that are related to the collaborative simulation of complex space systems involved in the exploration of our solar system. Currently, the NASA centers that are actively participating in the IMSim project are the Ames Research Center, the Jet Propulsion Laboratory (JPL), the Johnson Space Center (JSC), the Kennedy Space Center, the Langley Research Center and the Marshall Space Flight Center. In concept, each center participating in IMSim has its own set of simulation models and environment(s). These simulation tools are used to build the various simulation products that are used for scientific investigation, engineering analysis, system design, training, planning, operations and more. Working individually, these production simulations provide important data to various NASA projects.

  5. Dynamics of water clusters confined in proteins: a molecular dynamics simulation study of interfacial waters in a dimeric hemoglobin.

    Science.gov (United States)

    Gnanasekaran, Ramachandran; Xu, Yao; Leitner, David M

    2010-12-23

    Water confined in proteins exhibits dynamics distinct from the dynamics of water in the bulk or near the surface of a biomolecule. We examine the water dynamics at the interface of the two globules of the homodimeric hemoglobin from Scapharca inaequivalvis (HbI) by molecular dynamics (MD) simulations, with focus on water-protein hydrogen bond lifetimes and rotational anisotropy of the interfacial waters. We find that relaxation of the waters at the interface of both deoxy- and oxy-HbI, which contain a cluster of 17 and 11 interfacial waters, respectively, is well described by stretched exponentials with exponents from 0.1 to 0.6 and relaxation times of tens to thousands of picoseconds. The interfacial water molecules of oxy-HbI exhibit slower rotational relaxation and hydrogen bond rearrangement than those of deoxy-HbI, consistent with an allosteric transition from unliganded to liganded conformers involving the expulsion of several water molecules from the interface. Though the interfacial waters are translationally and rotationally static on the picosecond time scale, they contribute to fast communication between the globules via vibrations. We find that the interfacial waters enhance vibrational energy transport across the interface by ≈10%.

  6. Balanced Cluster Head Selection Based on Modified k-Means in a Distributed Wireless Sensor Network

    OpenAIRE

    Periyasamy, Sasikumar; Khara, Sibaram; Thangavelu, Shankar

    2016-01-01

    A major problem with Wireless Sensor Networks (WSNs) is the maximization of effective network lifetime through minimization of energy usage in the network nodes. A modified k-means (Mk-means) algorithm for clustering was proposed which includes three cluster heads (simultaneously chosen) for each cluster. These cluster heads (CHs) use a load sharing mechanism to rotate as the active cluster head, which conserves residual energy of the nodes, thereby extending network lifetime. Moreover, it re...

  7. DISTRIBUTED CERTIFICATE AUTHORITY IN CLUSTER-BASED MANET USING MULTI SECRET SHARING SCHEME

    Directory of Open Access Journals (Sweden)

    Mohammed Azza

    2015-11-01

    Full Text Available Providing secure communications in mobile ad hoc networks (MANET is an important and difficult problem, due to a lack of a key management infrastructure. The authentication is an important security service in (MANETs. To provide a node authentication service we use a fully distributed certificate authorities (FDCA based on the threshold cryptography. In this paper we propose an efficient and verifiable multi secret sharing scheme in cluster-based MANET with a low computation system. Our scheme is based on the overdetermined linear system equation in Galois fields GF(2r. We have analyzed our scheme based on security and performance criteria, and compared with existing approaches. The efficiency of our proposed schemes was verified and evaluated by simulation. Simulation results show that this approach is scalable.

  8. Distributed Optimization based Dynamic Tariff for Congestion Management in Distribution Networks

    DEFF Research Database (Denmark)

    Huang, Shaojun; Wu, Qiuwei; Zhao, Haoran

    2017-01-01

    participate in congestion management, which gives more certainty and transparency compared to the normal DT method. With the DDT method, aggregators reveal their final aggregated plan and respect the plan during operation. By establishing an equivalent overall optimization, it is proven that the DDT method......This paper proposes a distributed optimization based dynamic tariff (DDT) method for congestion management in distribution networks with high penetration of electric vehicles (EVs) and heat pumps (HPs). The DDT method employs a decomposition based optimization method to have aggregators explicitly...

  9. [Research on distribution of patents' holders for Chinese herbal compounds in treating cardiovascular and cerebrovascular based on cluster analysis].

    Science.gov (United States)

    YANG, Xu-Jie; XIAO, Shi-Ying

    2015-09-01

    To discuss the distribution of patents' holders for Chinese herbal compounds in treating cardiovascular and cerebrovascular, the patents' holders for Chinese herbal compounds in treating cardiovascular and cerebrovascular were cluster analyzed by means of simple statistics and cluster analysis. Clustering variables were composed of patent applications, patent maintained number, related papers' quantity, etc. Chinese herbal compound patents' holders were divided into four categories according to their different scientific research and patent strength. It is the magic weapon for Chinese herbal compound patents' holders that have scientific research patents' transforming and make coordination of patent protection and scientific innovation.

  10. Managing distributed dynamic systems with spatial grasp technology

    CERN Document Server

    Sapaty, Peter Simon

    2017-01-01

    The book describes a novel ideology and supporting information technology for integral management of both civil and defence-orientated large, distributed dynamic systems. The approach is based on a high-level Spatial Grasp Language, SGL, expressing solutions in physical, virtual, executive and combined environments in the form of active self-evolving and self-propagating patterns spatially matching the systems to be created, modified and controlled. The communicating interpreters of SGL can be installed in key system points, which may be in large numbers (up to millions and billions) and represent equipped humans, robots, laptops, smartphones, smart sensors, etc. Operating under gestalt-inspired scenarios in SGL initially injected from any points, these systems can be effectively converted into goal-driven spatial machines (rather than computers as dealing with physical matter too) capable of responding to numerous challenges caused by growing world dynamics in the 21st century. Including numerous practical e...

  11. Kinetic energy distributions of molecular and cluster ions sputtered from self-assembled monolayers of octanethiol on gold

    International Nuclear Information System (INIS)

    Arezki, Bahia; Delcorte, Arnaud; Bertrand, Patrick

    2002-01-01

    Self-assembled monolayers (SAMs) of alkanethiols are an ideal model system to study the mechanisms that lead to emission of organic species under keV ion bombardment. In this contribution, we focus on the emission processes of gold-molecule cluster ions, which are not fully understood yet. To gain insights into these processes, monolayers of octanethiol CH 3 (CH 2 ) 7 SH adsorbed on gold are investigated using time-of-flight secondary ion mass spectrometry (ToF-SIMS). First, the static SIMS conditions are verified using the degradation of the SAM signals as a function of ion fluence. Second, the kinetic energy distributions (KEDs) of fragment, parent and cluster ions ejected upon 15 keV Ga + ion bombardment are measured. The peak maxima, FWHMs and high energy tails of the distributions are analyzed for Au-thiolate clusters, as well as thiol fragments. After calibration of the energy spectra using monoatomic ions, we find that the KEDs of all the clusters containing the thiolate molecule peak at about 1.2 eV. Besides, the distributions of the gold-molecule cluster ions including Au(M-H) 2 - , the most intense cluster peak in the spectrum, are significantly narrower than that of the hydrocarbon fragments

  12. A Novel Method of Statistical Line Loss Estimation for Distribution Feeders Based on Feeder Cluster and Modified XGBoost

    Directory of Open Access Journals (Sweden)

    Shouxiang Wang

    2017-12-01

    Full Text Available The estimation of losses of distribution feeders plays a crucial guiding role for the planning, design, and operation of a distribution system. This paper proposes a novel estimation method of statistical line loss of distribution feeders using the feeder cluster technique and modified eXtreme Gradient Boosting (XGBoost algorithm that is based on the characteristic data of feeders that are collected in the smart power distribution and utilization system. In order to enhance the applicability and accuracy of the estimation model, k-medoids algorithm with weighting distance for clustering distribution feeders is proposed. Meanwhile, a variable selection method for clustering distribution feeders is discussed, considering the correlation and validity of variables. This paper next modifies the XGBoost algorithm by adding a penalty function in consideration of the effect of the theoretical value to the loss function for the estimation of statistical line loss of distribution feeders. The validity of the proposed methodology is verified by 762 distribution feeders in the Shanghai distribution system. The results show that the XGBoost method has higher accuracy than decision tree, neural network, and random forests by comparison of Root Mean Square Error (RMSE, Mean Absolute Percentage Error (MAPE, and Absolute Percentage Error (APE indexes. In particular, the theoretical value can significantly improve the reasonability of estimated results.

  13. Dynamics of voids and clusters and fluctuations in the cosmic background radiation

    International Nuclear Information System (INIS)

    Salpeter, E.E.

    1983-01-01

    The author summarizes briefly calculations on spherically symmetric models without dissipation for the dynamical development of large voids and galaxy (super)clusters from small underdensities and overdensities, respectively, at the recombination era. Implications are mentioned and conjectures for more complex geometries are discussed. He infers the density fluctuations which must have been present just after the recombination era to produce some present-day configuration. Fluctuations in the present-day cosmic background radiation are related to this and their inferred amplitude depends very strongly on the present-day value of the cosmological density parameter. The relation to observed upper limits on these fluctuations are discussed. (Auth.)

  14. Internal dynamics of the radio-halo cluster A2219: A multi-wavelength analysis

    Science.gov (United States)

    Boschin, W.; Girardi, M.; Barrena, R.; Biviano, A.; Feretti, L.; Ramella, M.

    2004-03-01

    We present the results of the dynamical analysis of the rich, hot, and X-ray very luminous galaxy cluster A2219, containing a powerful diffuse radio-halo. Our analysis is based on new redshift data for 27 galaxies in the cluster region, measured from spectra obtained at the TNG, with the addition of other 105 galaxies recovered from reduction of CFHT archive data in a cluster region of ˜5 arcmin radius (˜ 0.8 h-1 Mpc ; at the cluster distance) centered on the cD galaxy. The investigation of the dynamical status is also performed using X-ray data stored in the Chandra archive. Further, valuable information comes from other bands - optical photometric, infrared, and radio data - which are analyzed and/or discussed, too. We find that A2219 appears as a peak in the velocity space at z=0.225, and select 113 cluster members. We compute a high value for the line-of-sight velocity dispersion, σv= 1438+109-86 km s-1, consistent with the high average X-ray temperature of 10.3 keV. If dynamical equilibrium is assumed, the virial theorem leads to M˜2.8× 1015 M⊙ ;sun for the global mass within the virial region. However, further investigation based on both optical and X-ray data shows significant signs of a young dynamical status. In fact, we find strong evidence for the elongation of the cluster in the SE-NW direction coupled with a significant velocity gradient, as well as for the presence of substructure both in optical data and X-ray data. Moreover, we point out the presence of several active galaxies. We discuss the results of our multi-wavelength investigation suggesting a complex merging scenario where the main, original structure is subject to an ongoing merger with a few clumps aligned in a filament in the foreground oriented in an oblique direction with respect to the line-of-sight. Our conclusion supports the view of the connection between extended radio emission and merging phenomena in galaxy clusters. Based on observations made on the island of La Palma

  15. Detecting brain dynamics during resting state: a tensor based evolutionary clustering approach

    Science.gov (United States)

    Al-sharoa, Esraa; Al-khassaweneh, Mahmood; Aviyente, Selin

    2017-08-01

    Human brain is a complex network with connections across different regions. Understanding the functional connectivity (FC) of the brain is important both during resting state and task; as disruptions in connectivity patterns are indicators of different psychopathological and neurological diseases. In this work, we study the resting state functional connectivity networks (FCNs) of the brain from fMRI BOLD signals. Recent studies have shown that FCNs are dynamic even during resting state and understanding the temporal dynamics of FCNs is important for differentiating between different conditions. Therefore, it is important to develop algorithms to track the dynamic formation and dissociation of FCNs of the brain during resting state. In this paper, we propose a two step tensor based community detection algorithm to identify and track the brain network community structure across time. First, we introduce an information-theoretic function to reduce the dynamic FCN and identify the time points that are similar topologically to combine them into a tensor. These time points will be used to identify the different FC states. Second, a tensor based spectral clustering approach is developed to identify the community structure of the constructed tensors. The proposed algorithm applies Tucker decomposition to the constructed tensors and extract the orthogonal factor matrices along the connectivity mode to determine the common subspace within each FC state. The detected community structure is summarized and described as FC states. The results illustrate the dynamic structure of resting state networks (RSNs), including the default mode network, somatomotor network, subcortical network and visual network.

  16. Fast Distributed Dynamics of Semantic Networks via Social Media.

    Science.gov (United States)

    Carrillo, Facundo; Cecchi, Guillermo A; Sigman, Mariano; Slezak, Diego Fernández

    2015-01-01

    We investigate the dynamics of semantic organization using social media, a collective expression of human thought. We propose a novel, time-dependent semantic similarity measure (TSS), based on the social network Twitter. We show that TSS is consistent with static measures of similarity but provides high temporal resolution for the identification of real-world events and induced changes in the distributed structure of semantic relationships across the entire lexicon. Using TSS, we measured the evolution of a concept and its movement along the semantic neighborhood, driven by specific news/events. Finally, we showed that particular events may trigger a temporary reorganization of elements in the semantic network.

  17. Fast Distributed Dynamics of Semantic Networks via Social Media

    Directory of Open Access Journals (Sweden)

    Facundo Carrillo

    2015-01-01

    Full Text Available We investigate the dynamics of semantic organization using social media, a collective expression of human thought. We propose a novel, time-dependent semantic similarity measure (TSS, based on the social network Twitter. We show that TSS is consistent with static measures of similarity but provides high temporal resolution for the identification of real-world events and induced changes in the distributed structure of semantic relationships across the entire lexicon. Using TSS, we measured the evolution of a concept and its movement along the semantic neighborhood, driven by specific news/events. Finally, we showed that particular events may trigger a temporary reorganization of elements in the semantic network.

  18. Characterization and application of microearthquake clusters to problems of scaling, fault zone dynamics, and seismic monitoring at Parkfield, California

    Energy Technology Data Exchange (ETDEWEB)

    Nadeau, Robert Michael [Univ. of California, Berkeley, CA (United States)

    1995-10-01

    This document contains information about the characterization and application of microearthquake clusters and fault zone dynamics. Topics discussed include: Seismological studies; fault-zone dynamics; periodic recurrence; scaling of microearthquakes to large earthquakes; implications of fault mechanics and seismic hazards; and wave propagation and temporal changes.

  19. Dynamics of fragment capture for cluster structures of weakly bound 7Li

    Directory of Open Access Journals (Sweden)

    Shrivastava A.

    2013-12-01

    Full Text Available Role of cluster structures of 7Li on reaction dynamics have been studied by performing exclusive measurements of prompt-γ rays from residues with scattered particles at energy, E/Vb = 1.6, with 198Pt target. Yields of the residues resulting after capture of t and 4,5,6He, corresponding to different excitation energies of the composite system were estimated. The results were compared with three body classical-dynamical model for breakup fusion, constrained by the measured fusion, α and t capture cross-sections. The cross-section of residues from capture of α and t agreed well with the prediction of the model showing dominance of the two step process - breakup fusion, while those from tightly bound 6He showed massive transfer to be the dominant mechanism.

  20. Ionic cluster size distributions of swollen nafion/sulfated beta-cyclodextrin membranes characterized by nuclear magnetic resonance cryoporometry.

    Science.gov (United States)

    Jeon, Jae-Deok; Kwak, Seung-Yeop

    2007-08-16

    Nafion/sb-CD membranes were prepared by mixing 5 wt% Nafion solution with H+-form sulfated beta-cyclodextrin (sb-CD), and their water uptakes, ion exchange capacities (IECs), and ionic cluster size distributions were measured. Gravimetric and thermogravimetric measurements showed that the water uptake of the membranes increased with increases in their sb-CD content. The IECs of the membrane were measured with acid-base titration and found to increase with increases in the sb-CD content, reaching 0.96 mequiv/g for NC5 ("NCx" denotes a Nafion/sb-CD composite membrane containing x wt% of sb-CD). The cluster-correlation peaks and ionic cluster size distributions of the water-swollen membranes were determined using small-angle X-ray scattering (SAXS) and 1H nuclear magnetic resonance (NMR) cryoporometry, respectively. The SAXS experiments confirmed that increases in the sb-CD content of the membranes shifted the maximum SAXS peaks to lower angles, indicating an increase in the cluster correlation peak. NMR cryoporometry is based on the theory of the melting point depression, Delta Tm, of a liquid confined within a pore, which is dependent on the pore diameter. The melting point depression was determined by analyzing the variation of the NMR signal intensity with temperature. Our analysis of the intensity-temperature (IT) curves showed that the ionic cluster size distribution gradually became broader with increases in the membrane sb-CD content due to the increased water content, indicating an increase in the ionic cluster size. This result indicates that the presence of sb-CD with its many sulfonic acid sites in the Nafion membranes results in increases in the ionic cluster size as well as in the water uptake and the IEC. We conclude that NMR cryoporometry provides a method for determining the ionic cluster size on the nanometer scale in an aqueous environment, which cannot be obtained using other methods.

  1. Automatic detection of arterial input function in dynamic contrast enhanced MRI based on affinity propagation clustering.

    Science.gov (United States)

    Shi, Lin; Wang, Defeng; Liu, Wen; Fang, Kui; Wang, Yi-Xiang J; Huang, Wenhua; King, Ann D; Heng, Pheng Ann; Ahuja, Anil T

    2014-05-01

    To automatically and robustly detect the arterial input function (AIF) with high detection accuracy and low computational cost in dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). In this study, we developed an automatic AIF detection method using an accelerated version (Fast-AP) of affinity propagation (AP) clustering. The validity of this Fast-AP-based method was proved on two DCE-MRI datasets, i.e., rat kidney and human head and neck. The detailed AIF detection performance of this proposed method was assessed in comparison with other clustering-based methods, namely original AP and K-means, as well as the manual AIF detection method. Both the automatic AP- and Fast-AP-based methods achieved satisfactory AIF detection accuracy, but the computational cost of Fast-AP could be reduced by 64.37-92.10% on rat dataset and 73.18-90.18% on human dataset compared with the cost of AP. The K-means yielded the lowest computational cost, but resulted in the lowest AIF detection accuracy. The experimental results demonstrated that both the AP- and Fast-AP-based methods were insensitive to the initialization of cluster centers, and had superior robustness compared with K-means method. The Fast-AP-based method enables automatic AIF detection with high accuracy and efficiency. Copyright © 2013 Wiley Periodicals, Inc.

  2. A Human Activity Recognition System Based on Dynamic Clustering of Skeleton Data

    Directory of Open Access Journals (Sweden)

    Alessandro Manzi

    2017-05-01

    Full Text Available Human activity recognition is an important area in computer vision, with its wide range of applications including ambient assisted living. In this paper, an activity recognition system based on skeleton data extracted from a depth camera is presented. The system makes use of machine learning techniques to classify the actions that are described with a set of a few basic postures. The training phase creates several models related to the number of clustered postures by means of a multiclass Support Vector Machine (SVM, trained with Sequential Minimal Optimization (SMO. The classification phase adopts the X-means algorithm to find the optimal number of clusters dynamically. The contribution of the paper is twofold. The first aim is to perform activity recognition employing features based on a small number of informative postures, extracted independently from each activity instance; secondly, it aims to assess the minimum number of frames needed for an adequate classification. The system is evaluated on two publicly available datasets, the Cornell Activity Dataset (CAD-60 and the Telecommunication Systems Team (TST Fall detection dataset. The number of clusters needed to model each instance ranges from two to four elements. The proposed approach reaches excellent performances using only about 4 s of input data (~100 frames and outperforms the state of the art when it uses approximately 500 frames on the CAD-60 dataset. The results are promising for the test in real context.

  3. A Survey of Energy Conservation Mechanisms for Dynamic Cluster Based Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Rabia Noor Enam

    2018-04-01

    Full Text Available WSN (Wireless Sensor Network is an emerging technology that has unlimited potential for numerous application areas including military, crisis management, environmental, transportation, medical, home/ city automations and smart spaces. But energy constrained nature of WSNs necessitates that their architecture and communicating protocols to be designed in an energy aware manner. Sensor data collection through clustering mechanisms has become a common strategy in WSN. This paper presents a survey report on the major perspectives with which energy conservation mechanisms has been proposed in dynamic cluster based WSNs so far. All the solutions discussed in this paper focus on the cluster based protocols only.We have covered a vast scale of existing energy efficient protocols and have categorized them in six categories. In the beginning of this paper the fundamentals of the energy constraint issues of WSNs have been discussed and an overview of the causes of energy consumptions at all layers of WSN has been given. Later in this paper several previously proposed energy efficient protocols of WSNs are presented.

  4. Cluster synchronization in the adaptive complex dynamical networks via a novel approach

    International Nuclear Information System (INIS)

    Wu Xiangjun; Lu Hongtao

    2011-01-01

    This Letter investigates cluster synchronization in the adaptive complex dynamical networks with nonidentical nodes by a local control method and a novel adaptive strategy for the coupling strengths of the networks. In this approach, the coupling strength of each node adjusts adaptively only based on the state information of its neighborhood. By means of the proposed scheme, the sufficient conditions for achieving cluster synchronization are derived analytically by utilizing Lyapunov stability theory. It is demonstrated that the synchronization performance is sensitively affected by the control gain, the inner-coupling matrix and the network topological structure. The numerical simulations are performed to verify the effectiveness of the theoretical results. - Highlights: → We present a more realistic adaptive complex network model with diverse nodes. → The local controllers are designed based the community structure of the network. → Each node's coupling strength adapts self only by the state of its neighborhood. → The synchronization effect is affected by the network structure and control gain. → The Cluster synchronization method is robust against noise perturbation.

  5. Multivariate cluster analysis of dynamic iodine-123 iodobenzamide SPET dopamine D{sub 2}receptor images in schizophrenia

    Energy Technology Data Exchange (ETDEWEB)

    Acton, P.D. [Inst. of Nuclear Medicine, Univ. Coll. London Medical School, London (United Kingdom); Pilowsky, L.S. [Institute of Psychiatry, London (United Kingdom); Costa, D.C. [Inst. of Nuclear Medicine, Univ. Coll. London Medical School, London (United Kingdom); Ell, P.J. [Inst. of Nuclear Medicine, Univ. Coll. London Medical School, London (United Kingdom)

    1997-02-01

    This paper describes the application of a multivariate statistical technique to investigate striatal dopamine D{sub 2}receptor concentrations measured by iodine-123 iodobenzamide ({sup 123}I-IBZM) single-photon emission tomography (SPET). This technique enables the automatic segmentation of dynamic nuclear medicine images based on the underlying time-activity curves present in the data. Once the time-activity curves have been extracted, each pixel can be mapped back on to the underlying distribution, considerably reducing image noise. Cluster analysis has been verified using computer simulations and phantom studies. The technique has been applied to SPET images of dopamine D {sub 2}receptors in a total of 20 healthy and 20 schizophrenic volunteers (22 male, 18 female), using the ligand {sup 123}I-IBZM. Following automatic image segmentation, the concentration of striatal dopamine D {sub 2}receptors shows a significant left-sided asymmetry in male schizophrenics compared with male controls. The mean left-minus-right laterality index for controls is -1.52 (95% CI -3.72-0.66) and for patients 4.04 (95% CI 1.07-7.01). Analysis of variance shows a case-by-sex-by-side interaction, with F=10.01, P=0.005. We can now demonstrate that the previously observed male sex-specific D {sub 2}receptor asymmetry in schizophrenia, which had failed to attain statistical significance, is valid. Cluster analysis of dynamic nuclear medicine studies provides a powerful tool for automatic segmentation and noise reduction of the images, removing much of the subjectivity inherent in region-of-interest analysis. The observed striatal D {sub 2}asymmetry could reflect long hypothesized disruptions in dopamine-rich cortico-striatal-limbic circuits in schizophrenic males. (orig.). With 4 figs., 2 tabs.

  6. MAS-based Distributed Coordinated Control and Optimization in Microgrid and Microgrid Clusters: A Comprehensive Overview

    DEFF Research Database (Denmark)

    Han, Yang; Zhang, Ke; Hong, Li

    2018-01-01

    the power and energy, stabilize voltage and frequency, achieve economic and coordinated operation among the MGs and MGCs. However, the complex and diverse combinations of distributed generations in multi-agent system increase the complexity of system control and operation. In order to design the optimized...... the consensus is a vital problem in the complex dynamical systems, the distributed MAS-based consensus protocols are systematically reviewed. On the other hand, the communication delay issue, which is inevitable no matter in the low- or high-bandwidth communication networks, is crucial to maintain stability...... of the MGs and MGCs with fixed and random delays. Various control strategies to compensate the effect of communication delays have been reviewed, such as the neural network-based predictive control, the weighted average predictive control, the gain scheduling scheme and synchronization schemes based...

  7. Dynamic clustering and dispersion of lipid rafts contribute to fusion competence of myogenic cells

    International Nuclear Information System (INIS)

    Mukai, Atsushi; Kurisaki, Tomohiro; Sato, Satoshi B.; Kobayashi, Toshihide; Kondoh, Gen; Hashimoto, Naohiro

    2009-01-01

    Recent research indicates that the leading edge of lamellipodia of myogenic cells (myoblasts and myotubes) contains presumptive fusion sites, yet the mechanisms that render the plasma membrane fusion-competent remain largely unknown. Here we show that dynamic clustering and dispersion of lipid rafts contribute to both cell adhesion and plasma membrane union during myogenic cell fusion. Adhesion-complex proteins including M-cadherin, β-catenin, and p120-catenin accumulated at the leading edge of lamellipodia, which contains the presumptive fusion sites of the plasma membrane, in a lipid raft-dependent fashion prior to cell contact. In addition, disruption of lipid rafts by cholesterol depletion directly prevented the membrane union of myogenic cell fusion. Time-lapse recording showed that lipid rafts were laterally dispersed from the center of the lamellipodia prior to membrane fusion. Adhesion proteins that had accumulated at lipid rafts were also removed from the presumptive fusion sites when lipid rafts were laterally dispersed. The resultant lipid raft- and adhesion complex-free area at the leading edge fused with the opposing plasma membrane. These results demonstrate a key role for dynamic clustering/dispersion of lipid rafts in establishing fusion-competent sites of the myogenic cell membrane, providing a novel mechanistic insight into the regulation of myogenic cell fusion.

  8. Dynamic clustering and dispersion of lipid rafts contribute to fusion competence of myogenic cells

    Energy Technology Data Exchange (ETDEWEB)

    Mukai, Atsushi [Department of Regenerative Medicine, National Institute for Longevity Sciences, National Center for Geriatrics and Gerontology, 36-3 Gengo, Morioka, Oobu, Aichi 474-8522 (Japan); Kurisaki, Tomohiro [Department of Growth Regulation, Institute for Frontier Medical Sciences, Kyoto University, 53 Shogoin-Kawahara-cho, Sakyo-ku, Kyoto 606-8507 (Japan); Sato, Satoshi B. [Research Center for Low Temperature and Material Sciences, Kyoto University, Yoshida-honmachi, Kyoto 606-8501 (Japan); Kobayashi, Toshihide [Lipid Biology Laboratory, Discovery Research Institute, RIKEN, Wako, Saitama 351-0198 (Japan); Kondoh, Gen [Laboratory of Animal Experiments for Regeneration, Institute for Frontier Medical Sciences, Kyoto University, 53 Shogoin-Kawahara-cho, Sakyo-ku, Kyoto 606-8507 (Japan); Hashimoto, Naohiro, E-mail: nao@nils.go.jp [Department of Regenerative Medicine, National Institute for Longevity Sciences, National Center for Geriatrics and Gerontology, 36-3 Gengo, Morioka, Oobu, Aichi 474-8522 (Japan)

    2009-10-15

    Recent research indicates that the leading edge of lamellipodia of myogenic cells (myoblasts and myotubes) contains presumptive fusion sites, yet the mechanisms that render the plasma membrane fusion-competent remain largely unknown. Here we show that dynamic clustering and dispersion of lipid rafts contribute to both cell adhesion and plasma membrane union during myogenic cell fusion. Adhesion-complex proteins including M-cadherin, {beta}-catenin, and p120-catenin accumulated at the leading edge of lamellipodia, which contains the presumptive fusion sites of the plasma membrane, in a lipid raft-dependent fashion prior to cell contact. In addition, disruption of lipid rafts by cholesterol depletion directly prevented the membrane union of myogenic cell fusion. Time-lapse recording showed that lipid rafts were laterally dispersed from the center of the lamellipodia prior to membrane fusion. Adhesion proteins that had accumulated at lipid rafts were also removed from the presumptive fusion sites when lipid rafts were laterally dispersed. The resultant lipid raft- and adhesion complex-free area at the leading edge fused with the opposing plasma membrane. These results demonstrate a key role for dynamic clustering/dispersion of lipid rafts in establishing fusion-competent sites of the myogenic cell membrane, providing a novel mechanistic insight into the regulation of myogenic cell fusion.

  9. Cluster dynamics modeling of Mn-Ni-Si precipitates in ferritic-martensitic steel under irradiation

    Science.gov (United States)

    Ke, Jia-Hong; Ke, Huibin; Odette, G. Robert; Morgan, Dane

    2018-01-01

    Mn-Ni-Si precipitates (MNSPs) are known to be responsible for irradiation-induced hardening and embrittlement in structural alloys used in nuclear reactors. Studies have shown that precipitation of the MNSPs in 9-Cr ferritic-martensitic (F-M) alloys, such as T91, is strongly associated with heterogeneous nucleation on dislocations, coupled with radiation-induced solute segregation to these sinks. Therefore it is important to develop advanced predictive models for Mn-Ni-Si precipitation in F-M alloys under irradiation based on an understanding of the underlying mechanisms. Here we use a cluster dynamics model, which includes multiple effects of dislocations, to study the evolution of MNSPs in a commercial F-M alloy T91. The model predictions are calibrated by data from proton irradiation experiments at 400 °C. Radiation induced solute segregation at dislocations is evaluated by a continuum model that is integrated into the cluster dynamics simulations, including the effects of dislocations as heterogeneous nucleation sites. The result shows that MNSPs in T91 are primarily irradiation-induced and, in particular, both heterogeneous nucleation and radiation-induced segregation at dislocations are necessary to rationalize the experimental observations.

  10. The Dynamics of the Globular Star Cluster 47 TUC (NGC 104)

    Science.gov (United States)

    Murphy, B. W.; Moore, C. A.; Trotter, T. E.; Cohn, H. N.; Lugger, P. M.

    1998-12-01

    We have fit dynamically evolving Fokker-Planck models to the globular star cluster 47 Tuc (Ngc 104). Using mass-function and star-count data from the Hubble Space Telescope, we have determined the global stellar mass function down to 0.1 Msun. In addition to the mass function and star-count data, the velocity-dispersion profile and millisecond pulsar acceleration are well fit by the model. The best-fitting model is a pre-core-collapse model that mimics the behavior of a cluster with a sizable population of primordial binaries. These Fokker-Planck models are far more successful than are King-Mitchie model for fitting the full set of observational data. The best-fitting model has a mass function with power-law indices of 1.35, -1.0, 0.5, and -1.0 (where 1.35 is the Salpeter index) over the mass intervals of 60 to 1.0 Msun, 1.0 to 0.55 Msun, 0.55 to 0.25 Msun, and 0.35 to 0.1 Msun, respectively. The total mass of the cluster is 1.1x 10(6) Msun, the half-mass radius is 7 parsecs, and the core radius is 0.2 parsecs. The model contains a large number (4.6% of the total cluster mass) in nonluminous objects of 1.4 Msun. If most of these objects are neutron stars, the large inferred number suggest that either the upper main sequence mass function was flatter that the Salpeter mass function or that the progenitor stellar mass range for neutron star formation may extend to lower masses in low-metallicity systems than in high metallicity systems.

  11. U1 snDNA clusters in grasshoppers: chromosomal dynamics and genomic organization.

    Science.gov (United States)

    Anjos, A; Ruiz-Ruano, F J; Camacho, J P M; Loreto, V; Cabrero, J; de Souza, M J; Cabral-de-Mello, D C

    2015-02-01

    The spliceosome, constituted by a protein set associated with small nuclear RNA (snRNA), is responsible for mRNA maturation through intron removal. Among snRNA genes, U1 is generally a conserved repetitive sequence. To unveil the chromosomal/genomic dynamics of this multigene family in grasshoppers, we mapped U1 genes by fluorescence in situ hybridization in 70 species belonging to the families Proscopiidae, Pyrgomorphidae, Ommexechidae, Romaleidae and Acrididae. Evident clusters were observed in all species, indicating that, at least, some U1 repeats are tandemly arrayed. High conservation was observed in the first four families, with most species carrying a single U1 cluster, frequently located in the third or fourth longest autosome. By contrast, extensive variation was observed among Acrididae, from a single chromosome pair carrying U1 to all chromosome pairs carrying it, with occasional occurrence of two or more clusters in the same chromosome. DNA sequence analysis in Eyprepocnemis plorans (species carrying U1 clusters on seven different chromosome pairs) and Locusta migratoria (carrying U1 in a single chromosome pair) supported the coexistence of functional and pseudogenic lineages. One of these pseudogenic lineages was truncated in the same nucleotide position in both species, suggesting that it was present in a common ancestor to both species. At least in E. plorans, this U1 snDNA pseudogenic lineage was associated with 5S rDNA and short interspersed elements (SINE)-like mobile elements. Given that we conclude in grasshoppers that the U1 snDNA had evolved under the birth-and-death model and that its intragenomic spread might be related with mobile elements.

  12. U1 snDNA clusters in grasshoppers: chromosomal dynamics and genomic organization

    Science.gov (United States)

    Anjos, A; Ruiz-Ruano, F J; Camacho, J P M; Loreto, V; Cabrero, J; de Souza, M J; Cabral-de-Mello, D C

    2015-01-01

    The spliceosome, constituted by a protein set associated with small nuclear RNA (snRNA), is responsible for mRNA maturation through intron removal. Among snRNA genes, U1 is generally a conserved repetitive sequence. To unveil the chromosomal/genomic dynamics of this multigene family in grasshoppers, we mapped U1 genes by fluorescence in situ hybridization in 70 species belonging to the families Proscopiidae, Pyrgomorphidae, Ommexechidae, Romaleidae and Acrididae. Evident clusters were observed in all species, indicating that, at least, some U1 repeats are tandemly arrayed. High conservation was observed in the first four families, with most species carrying a single U1 cluster, frequently located in the third or fourth longest autosome. By contrast, extensive variation was observed among Acrididae, from a single chromosome pair carrying U1 to all chromosome pairs carrying it, with occasional occurrence of two or more clusters in the same chromosome. DNA sequence analysis in Eyprepocnemis plorans (species carrying U1 clusters on seven different chromosome pairs) and Locusta migratoria (carrying U1 in a single chromosome pair) supported the coexistence of functional and pseudogenic lineages. One of these pseudogenic lineages was truncated in the same nucleotide position in both species, suggesting that it was present in a common ancestor to both species. At least in E. plorans, this U1 snDNA pseudogenic lineage was associated with 5S rDNA and short interspersed elements (SINE)-like mobile elements. Given that we conclude in grasshoppers that the U1 snDNA had evolved under the birth-and-death model and that its intragenomic spread might be related with mobile elements. PMID:25248465

  13. Para-hydrogen and helium cluster size distributions in free jet expansions based on Smoluchowski theory with kernel scaling.

    Science.gov (United States)

    Kornilov, Oleg; Toennies, J Peter

    2015-02-21

    The size distribution of para-H2 (pH2) clusters produced in free jet expansions at a source temperature of T0 = 29.5 K and pressures of P0 = 0.9-1.96 bars is reported and analyzed according to a cluster growth model based on the Smoluchowski theory with kernel scaling. Good overall agreement is found between the measured and predicted, Nk = A k(a) e(-bk), shape of the distribution. The fit yields values for A and b for values of a derived from simple collision models. The small remaining deviations between measured abundances and theory imply a (pH2)k magic number cluster of k = 13 as has been observed previously by Raman spectroscopy. The predicted linear dependence of b(-(a+1)) on source gas pressure was verified and used to determine the value of the basic effective agglomeration reaction rate constant. A comparison of the corresponding effective growth cross sections σ11 with results from a similar analysis of He cluster size distributions indicates that the latter are much larger by a factor 6-10. An analysis of the three body recombination rates, the geometric sizes and the fact that the He clusters are liquid independent of their size can explain the larger cross sections found for He.

  14. Para-hydrogen and helium cluster size distributions in free jet expansions based on Smoluchowski theory with kernel scaling

    Energy Technology Data Exchange (ETDEWEB)

    Kornilov, Oleg; Toennies, J. Peter [Max-Planck-Institut für Dynamik und Selbstorganisation, Am Fassberg 17, 37077 Göttingen (Germany)

    2015-02-21

    The size distribution of para-H{sub 2} (pH{sub 2}) clusters produced in free jet expansions at a source temperature of T{sub 0} = 29.5 K and pressures of P{sub 0} = 0.9–1.96 bars is reported and analyzed according to a cluster growth model based on the Smoluchowski theory with kernel scaling. Good overall agreement is found between the measured and predicted, N{sub k} = A k{sup a} e{sup −bk}, shape of the distribution. The fit yields values for A and b for values of a derived from simple collision models. The small remaining deviations between measured abundances and theory imply a (pH{sub 2}){sub k} magic number cluster of k = 13 as has been observed previously by Raman spectroscopy. The predicted linear dependence of b{sup −(a+1)} on source gas pressure was verified and used to determine the value of the basic effective agglomeration reaction rate constant. A comparison of the corresponding effective growth cross sections σ{sub 11} with results from a similar analysis of He cluster size distributions indicates that the latter are much larger by a factor 6-10. An analysis of the three body recombination rates, the geometric sizes and the fact that the He clusters are liquid independent of their size can explain the larger cross sections found for He.

  15. CHEMICAL ABUNDANCES IN NGC 5053: A VERY METAL-POOR AND DYNAMICALLY COMPLEX GLOBULAR CLUSTER

    Energy Technology Data Exchange (ETDEWEB)

    Boberg, Owen M.; Friel, Eileen D.; Vesperini, Enrico [Astronomy Department, Indiana University, Bloomington, IN 47405 (United States)

    2015-05-10

    NGC 5053 provides a rich environment to test our understanding of the complex evolution of globular clusters (GCs). Recent studies have found that this cluster has interesting morphological features beyond the typical spherical distribution of GCs, suggesting that external tidal effects have played an important role in its evolution and current properties. Additionally, simulations have shown that NGC 5053 could be a likely candidate to belong to the Sagittarius dwarf galaxy (Sgr dSph) stream. Using the Wisconsin–Indiana–Yale–NOAO–Hydra multi-object spectrograph, we have collected high quality (signal-to-noise ratio ∼ 75–90), medium-resolution spectra for red giant branch stars in NGC 5053. Using these spectra we have measured the Fe, Ca, Ti, Ni, Ba, Na, and O abundances in the cluster. We measure an average cluster [Fe/H] abundance of −2.45 with a standard deviation of 0.04 dex, making NGC 5053 one of the most metal-poor GCs in the Milky Way (MW). The [Ca/Fe], [Ti/Fe], and [Ba/Fe] we measure are consistent with the abundances of MW halo stars at a similar metallicity, with alpha-enhanced ratios and slightly depleted [Ba/Fe]. The Na and O abundances show the Na–O anti-correlation found in most GCs. From our abundance analysis it appears that NGC 5053 is at least chemically similar to other GCs found in the MW. This does not, however, rule out NGC 5053 being associated with the Sgr dSph stream.

  16. Chemical Abundances in NGC 5053: A Very Metal-poor and Dynamically Complex Globular Cluster

    Science.gov (United States)

    Boberg, Owen M.; Friel, Eileen D.; Vesperini, Enrico

    2015-05-01

    NGC 5053 provides a rich environment to test our understanding of the complex evolution of globular clusters (GCs). Recent studies have found that this cluster has interesting morphological features beyond the typical spherical distribution of GCs, suggesting that external tidal effects have played an important role in its evolution and current properties. Additionally, simulations have shown that NGC 5053 could be a likely candidate to belong to the Sagittarius dwarf galaxy (Sgr dSph) stream. Using the Wisconsin-Indiana-Yale-NOAO-Hydra multi-object spectrograph, we have collected high quality (signal-to-noise ratio ˜ 75-90), medium-resolution spectra for red giant branch stars in NGC 5053. Using these spectra we have measured the Fe, Ca, Ti, Ni, Ba, Na, and O abundances in the cluster. We measure an average cluster [Fe/H] abundance of -2.45 with a standard deviation of 0.04 dex, making NGC 5053 one of the most metal-poor GCs in the Milky Way (MW). The [Ca/Fe], [Ti/Fe], and [Ba/Fe] we measure are consistent with the abundances of MW halo stars at a similar metallicity, with alpha-enhanced ratios and slightly depleted [Ba/Fe]. The Na and O abundances show the Na-O anti-correlation found in most GCs. From our abundance analysis it appears that NGC 5053 is at least chemically similar to other GCs found in the MW. This does not, however, rule out NGC 5053 being associated with the Sgr dSph stream.

  17. Molecular dynamics simulations to examine structure, energetics, and evaporation/condensation dynamics in small charged clusters of water or methanol containing a single monatomic ion.

    Science.gov (United States)

    Daub, Christopher D; Cann, Natalie M

    2012-11-01

    We study small clusters of water or methanol containing a single Ca(2+), Na(+), or Cl(-) ion with classical molecular dynamics simulations, using models that incorporate polarizability via the Drude oscillator framework. Evaporation and condensation of solvent from these clusters is examined in two systems, (1) for isolated clusters initially prepared at different temperatures and (2) those with a surrounding inert (Ar) gas of varying temperature. We examine these clusters over a range of sizes, from almost bare ions up to 40 solvent molecules. We report data on the evaporation and condensation of solvent from the clusters and argue that the observed temperature dependence of evaporation in the smallest clusters demonstrates that the presence of heated gas alone cannot, in most cases, solely account for bare ion production in electrospray ionization (ESI), neglecting the key contribution of the electric field. We also present our findings on the structure and energetics of the clusters as a function of size. Our data agree well with the abundant literature on hydrated ion clusters and offer some novel insight into the structure of methanol and ion clusters, especially those with a Cl(-) anion, where we observe the presence of chain-like structures of methanol molecules. Finally, we provide some data on the reparameterizations necessary to simulate ions in methanol using the separately developed Drude oscillator models for methanol and for ions in water.

  18. EXTRACTION OF THE MEAN RADIAL MASS-DISTRIBUTION IN CLUSTERS OF GALAXIES BY OBSERVATIONS OF WEAK GRAVITATIONAL IMAGING

    NARCIS (Netherlands)

    BREIMER, TG

    The gravitational fields of clusters of galaxies cause systematic distortions of the images of background galaxies. Recently, the lens inversion problem, reconstruction of the mean surface density distribution in the lens from the pattern of systematic distortions, has been the object of several

  19. 2nd International Symposium "Atomic Cluster Collisions : Structure and Dynamics from the Nuclear to the Biological Scale"

    CERN Document Server

    Solov'yov, Andrey; ISACC 2007; Latest advances in atomic cluster collisions

    2008-01-01

    This book presents a 'snapshot' of the most recent and significant advances in the field of cluster physics. It is a comprehensive review based on contributions by the participants of the 2nd International Symposium on Atomic Cluster Collisions (ISACC 2007) held in July 19-23, 2007 at GSI, Darmstadt, Germany. The purpose of the Symposium is to promote the growth and exchange of scientific information on the structure and properties of nuclear, atomic, molecular, biological and complex cluster systems studied by means of photonic, electronic, heavy particle and atomic collisions. Particular attention is devoted to dynamic phenomena, many-body effects taking place in cluster systems of a different nature - these include problems of fusion and fission, fragmentation, collective electron excitations, phase transitions, etc.Both the experimental and theoretical aspects of cluster physics, uniquely placed between nuclear physics on the one hand and atomic, molecular and solid state physics on the other, are discuss...

  20. Linking Dynamic Habitat Selection with Wading Bird Foraging Distributions across Resource Gradients.

    Directory of Open Access Journals (Sweden)

    James M Beerens

    Full Text Available Species distribution models (SDM link species occurrence with a suite of environmental predictors and provide an estimate of habitat quality when the variable set captures the biological requirements of the species. SDMs are inherently more complex when they include components of a species' ecology such as conspecific attraction and behavioral flexibility to exploit resources that vary across time and space. Wading birds are highly mobile, demonstrate flexible habitat selection, and respond quickly to changes in habitat quality; thus serving as important indicator species for wetland systems. We developed a spatio-temporal, multi-SDM framework using Great Egret (Ardea alba, White Ibis (Eudocimus albus, and Wood Stork (Mycteria Americana distributions over a decadal gradient of environmental conditions to predict species-specific abundance across space and locations used on the landscape over time. In models of temporal dynamics, species demonstrated conditional preferences for resources based on resource levels linked to differing temporal scales. Wading bird abundance was highest when prey production from optimal periods of inundation was concentrated in shallow depths. Similar responses were observed in models predicting locations used over time, accounting for spatial autocorrelation. Species clustered in response to differing habitat conditions, indicating that social attraction can co-vary with foraging strategy, water-level changes, and habitat quality. This modeling framework can be applied to evaluate the multi-annual resource pulses occurring in real-time, climate change scenarios, or restorative hydrological regimes by tracking changing seasonal and annual distribution and abundance of high quality foraging patches.

  1. Distributed dynamical computation in neural circuits with propagating coherent activity patterns.

    Directory of Open Access Journals (Sweden)

    Pulin Gong

    2009-12-01

    Full Text Available Activity in neural circuits is spatiotemporally organized. Its spatial organization consists of multiple, localized coherent patterns, or patchy clusters. These patterns propagate across the circuits over time. This type of collective behavior has ubiquitously been observed, both in spontaneous activity and evoked responses; its function, however, has remained unclear. We construct a spatially extended, spiking neural circuit that generates emergent spatiotemporal activity patterns, thereby capturing some of the complexities of the patterns observed empirically. We elucidate what kind of fundamental function these patterns can serve by showing how they process information. As self-sustained objects, localized coherent patterns can signal information by propagating across the neural circuit. Computational operations occur when these emergent patterns interact, or collide with each other. The ongoing behaviors of these patterns naturally embody both distributed, parallel computation and cascaded logical operations. Such distributed computations enable the system to work in an inherently flexible and efficient way. Our work leads us to propose that propagating coherent activity patterns are the underlying primitives with which neural circuits carry out distributed dynamical computation.

  2. Linking dynamic habitat selection with wading bird foraging distributions across resource gradients

    Science.gov (United States)

    Beerens, James M.; Noonberg, Erik G.; Gawlik, Dale E.

    2015-01-01

    Species distribution models (SDM) link species occurrence with a suite of environmental predictors and provide an estimate of habitat quality when the variable set captures the biological requirements of the species. SDMs are inherently more complex when they include components of a species' ecology such as conspecific attraction and behavioral flexibility to exploit resources that vary across time and space. Wading birds are highly mobile, demonstrate flexible habitat selection, and respond quickly to changes in habitat quality; thus serving as important indicator species for wetland systems. We developed a spatio-temporal, multi-SDM framework using Great Egret (Ardea alba), White Ibis (Eudocimus albus), and Wood Stork (Mycteria Americana) distributions over a decadal gradient of environmental conditions to predict species-specific abundance across space and locations used on the landscape over time. In models of temporal dynamics, species demonstrated conditional preferences for resources based on resource levels linked to differing temporal scales. Wading bird abundance was highest when prey production from optimal periods of inundation was concentrated in shallow depths. Similar responses were observed in models predicting locations used over time, accounting for spatial autocorrelation. Species clustered in response to differing habitat conditions, indicating that social attraction can co-vary with foraging strategy, water-level changes, and habitat quality. This modeling framework can be applied to evaluate the multi-annual resource pulses occurring in real-time, climate change scenarios, or restorative hydrological regimes by tracking changing seasonal and annual distribution and abundance of high quality foraging patches.

  3. Distributed Dynamic Host Configuration Protocol (D2HCP).

    Science.gov (United States)

    Villalba, Luis Javier García; Matesanz, Julián García; Orozco, Ana Lucila Sandoval; Díaz, José Duván Márquez

    2011-01-01

    Mobile Ad Hoc Networks (MANETs) are multihop wireless networks of mobile nodes without any fixed or preexisting infrastructure. The topology of these networks can change randomly due to the unpredictable mobility of nodes and their propagation characteristics. In most networks, including MANETs, each node needs a unique identifier to communicate. This work presents a distributed protocol for dynamic node IP address assignment in MANETs. Nodes of a MANET synchronize from time to time to maintain a record of IP address assignments in the entire network and detect any IP address leaks. The proposed stateful autoconfiguration scheme uses the OLSR proactive routing protocol for synchronization and guarantees unique IP addresses under a variety of network conditions, including message losses and network partitioning. Simulation results show that the protocol incurs low latency and communication overhead for IP address assignment.

  4. THE DYNAMICS OF A DISTRIBUTION SYSTEM SIMULATED ON A SPREADSHEET

    Directory of Open Access Journals (Sweden)

    R. Reinecke

    2012-01-01

    Full Text Available

    ENGLISH ABSTRACT: The dynamics of a typical production-distribution system, namely from manufacturer to distributors to retailers has been simulated with the aid of Lotus 123 on a personal computer. The original simulation program DYNAr10 was run on an IBM 1620 mainframe computer but we successfully converted it to run on a personal computer using LOTUS 123.
    This paper deals with problems encountered in using the present MS-DOS limited PC machines to run application programmes written for earlier mainframe machines. It is also shown that results very comparable with those obtained on mainframe machines can be generated on a simple PC.

    AFRIKAANSE OPSOMMING: Hierdie referaat beskryf die ervaring van magisterstudente met die omskakeling van die simulasieprogram DYNAMO vir die ondersoek van die dinamika van industriele stelsels van hoofraamrekenaar na 'n persoonlike rekenaar.

  5. Preferential segregation of Pd atoms in the Ag-Pd bimetallic cluster: Density functional theory and molecular dynamics simulation

    Science.gov (United States)

    Kim, Hyun You; Kim, Hyoung Gyu; Ryu, Ji Hoon; Lee, Hyuck Mo

    2007-06-01

    Classical molecular dynamics simulations of the coalescence between an Ag cluster composed of 135 atoms and a Pd cluster of 16 atoms were performed at 500K . All Pd atoms penetrated into the Ag cluster and preferentially segregated at the subsurface layer. The density functional theory calculations revealed that the center site is the most stable position for Pd atoms. However, the energy barrier for further penetration of Pd atoms located at the subsurface was too high to overcome, and thus a metastable structure with Pd atoms segregated at the subsurface did not evolve.

  6. Study of ice cluster impacts on amorphous silica using the ReaxFF reactive force field molecular dynamics simulation method

    Energy Technology Data Exchange (ETDEWEB)

    Rahnamoun, A. [Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, 234 Research East, University Park, Pennsylvania 16802 (United States); Duin, A. C. T. van [Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, 240 Research East, University Park, Pennsylvania 16802 (United States)

    2016-03-07

    We study the dynamics of the collisions between amorphous silica structures and amorphous and crystal ice clusters with impact velocities of 1 km/s, 4 km/s, and 7 km/s using the ReaxFF reactive molecular dynamics simulation method. The initial ice clusters consist of 150 water molecules for the amorphous ice cluster and 128 water molecules for the crystal ice cluster. The ice clusters are collided on the surface of amorphous fully oxidized and suboxide silica. These simulations show that at 1 km/s impact velocities, all the ice clusters accumulate on the surface and at 4 km/s and 7 km/s impact velocities, some of the ice cluster molecules bounce back from the surface. At 4 km/s and 7 km/s impact velocities, few of the water molecules dissociations are observed. The effect of the second ice cluster impacts on the surfaces which are fully covered with ice, on the mass loss/accumulation is studied. These studies show that at 1 km/s impacts, the entire ice cluster accumulates on the surface at both first and second ice impacts. At higher impact velocities, some ice molecules which after the first ice impacts have been attached to the surface will separate from the surface after the second ice impacts at 7 km/s impact velocity. For the 4 km/s ice cluster impact, ice accumulation is observed for the crystal ice cluster impacts and ice separation is observed for the amorphous ice impacts. Observing the temperatures of the ice clusters during the collisions indicates that the possibility of electron excitement at impact velocities less than 10 km/s is minimal and ReaxFF reactive molecular dynamics simulation can predict the chemistry of these hypervelocity impacts. However, at impact velocities close to 10 km/s the average temperature of the impacting ice clusters increase to about 2000 K, with individual molecules occasionally reaching temperatures of over 8000 K and thus it will be prudent to consider the concept of electron excitation at

  7. Statics and Dynamics of Selfish Interactions in Distributed Service Systems.

    Directory of Open Access Journals (Sweden)

    Fabrizio Altarelli

    Full Text Available We study a class of games which models the competition among agents to access some service provided by distributed service units and which exhibits congestion and frustration phenomena when service units have limited capacity. We propose a technique, based on the cavity method of statistical physics, to characterize the full spectrum of Nash equilibria of the game. The analysis reveals a large variety of equilibria, with very different statistical properties. Natural selfish dynamics, such as best-response, usually tend to large-utility equilibria, even though those of smaller utility are exponentially more numerous. Interestingly, the latter actually can be reached by selecting the initial conditions of the best-response dynamics close to the saturation limit of the service unit capacities. We also study a more realistic stochastic variant of the game by means of a simple and effective approximation of the average over the random parameters, showing that the properties of the average-case Nash equilibria are qualitatively similar to the deterministic ones.

  8. Hematopoietic lineage distribution and evolutionary dynamics of clonal hematopoiesis.

    Science.gov (United States)

    Arends, Christopher Maximilian; Galan-Sousa, Joel; Hoyer, Kaja; Chan, Willy; Jäger, Marten; Yoshida, Kenichi; Seemann, Ricarda; Noerenberg, Daniel; Waldhueter, Nils; Fleischer-Notter, Helga; Christen, Friederike; Schmitt, Clemens A; Dörken, Bernd; Pelzer, Uwe; Sinn, Marianne; Zemojtel, Tomasz; Ogawa, Seishi; Märdian, Sven; Schreiber, Adrian; Kunitz, Annegret; Krüger, Ulrike; Bullinger, Lars; Mylonas, Elena; Frick, Mareike; Damm, Frederik

    2018-03-01

    Clonal hematopoiesis of indeterminate potential (CHIP) occurs in an age-related manner and associates with an increased risk of hematologic cancer, atherosclerotic disease, and shorter overall survival. Little is known about the cell of origin, repartition patterns of clonal mutations within the hematopoietic differentiation tree, and its dynamics under evolutionary pressure. Using targeted sequencing, CHIP was identified in 121 out of 437 elderly individuals (27.7%). Variant allele frequencies (VAFs) of 91 mutations were studied in six peripheral blood cell fractions. VAFs were significantly higher in monocytes, granulocytes, and NK-cells compared to B- or T cells. In all cases with available bone marrow material, mutations could be identified in Lin - CD34 + CD38 - HSCs with subsequent expansion to myeloid primed progenitors. In 22 patients with solid cancer receiving (radio-)chemotherapy, longitudinal study of 32 mutations at 121 time points identified relative VAF changes of at least 50% in 13/32 mutations. VAFs of DNMT3A, were stable in 12/13 cases (P < .001). Cancer patients with a clonal mutation other than DNMT3A required more often red blood cell transfusions and dose reductions. Our results provide novel insights into cellular distribution of clonal mutations, their dynamics under chemotherapy, and advocate for systematic analyses for CHIP in cancer patients.

  9. Patterns of inequality: Dynamics of income distribution in USA and global energy consumption distribution

    Science.gov (United States)

    Banerjee, Anand; Yakovenko, Victor

    2010-03-01

    Applying the principle of entropy maximization, we argued that the distribution of money in a closed economic system should be exponential [1], see also recent review [2]. In this talk, we show that income distribution in USA is exponential for the majority of population (about 97%). However, the high-income tail follows a power law and is highly dynamical, i.e., out of equilibrium. The fraction of income going to the tail swelled to 20% of all income in 2000 and 2006 at the peaks of speculative bubbles followed by spectacular crashes. Next, we analyze the global distribution of energy consumption per capita among different countries. In the first approximation, it is reasonably well captured by the exponential function. Comparing the data for 1990 and 2005, we observe that the distribution is getting closer to the exponential, presumably as a result of globalization of the world economy.[4pt] [1] A. A. Dragulescu and V. M. Yakovenko, Eur. Phys. J. B 17, 723 (2000). [2] V. M. Yakovenko and J. B. Rosser, to appear in Rev. Mod. Phys. (2009), arXiv:0905.1518.

  10. Wealth distribution of simple exchange models coupled with extremal dynamics

    Science.gov (United States)

    Bagatella-Flores, N.; Rodríguez-Achach, M.; Coronel-Brizio, H. F.; Hernández-Montoya, A. R.

    2015-01-01

    Punctuated Equilibrium (PE) states that after long periods of evolutionary quiescence, species evolution can take place in short time intervals, where sudden differentiation makes new species emerge and some species extinct. In this paper, we introduce and study the effect of punctuated equilibrium on two different asset exchange models: the yard sale model (YS, winner gets a random fraction of a poorer player's wealth) and the theft and fraud model (TF, winner gets a random fraction of the loser's wealth). The resulting wealth distribution is characterized using the Gini index. In order to do this, we consider PE as a perturbation with probability ρ of being applied. We compare the resulting values of the Gini index at different increasing values of ρ in both models. We found that in the case of the TF model, the Gini index reduces as the perturbation ρ increases, not showing dependence with the agents number. While for YS we observe a phase transition which happens around ρc = 0.79. For perturbations ρ <ρc the Gini index reaches the value of one as time increases (an extreme wealth condensation state), whereas for perturbations greater than or equal to ρc the Gini index becomes different to one, avoiding the system reaches this extreme state. We show that both simple exchange models coupled with PE dynamics give more realistic results. In particular for YS, we observe a power low decay of wealth distribution.

  11. Mean, covariance, and effective dimension of stochastic distributed delay dynamics

    Science.gov (United States)

    René, Alexandre; Longtin, André

    2017-11-01

    Dynamical models are often required to incorporate both delays and noise. However, the inherently infinite-dimensional nature of delay equations makes formal solutions to stochastic delay differential equations (SDDEs) challenging. Here, we present an approach, similar in spirit to the analysis of functional differential equations, but based on finite-dimensional matrix operators. This results in a method for obtaining both transient and stationary solutions that is directly amenable to computation, and applicable to first order differential systems with either discrete or distributed delays. With fewer assumptions on the system's parameters than other current solution methods and no need to be near a bifurcation, we decompose the solution to a linear SDDE with arbitrary distributed delays into natural modes, in effect the eigenfunctions of the differential operator, and show that relatively few modes can suffice to approximate the probability density of solutions. Thus, we are led to conclude that noise makes these SDDEs effectively low dimensional, which opens the possibility of practical definitions of probability densities over their solution space.

  12. MonALISA: An agent based, dynamic service system to monitor, control and optimize distributed systems

    Science.gov (United States)

    Legrand, I.; Newman, H.; Voicu, R.; Cirstoiu, C.; Grigoras, C.; Dobre, C.; Muraru, A.; Costan, A.; Dediu, M.; Stratan, C.

    2009-12-01

    The MonALISA (Monitoring Agents in a Large Integrated Services Architecture) framework provides a set of distributed services for monitoring, control, management and global optimization for large scale distributed systems. It is based on an ensemble of autonomous, multi-threaded, agent-based subsystems which are registered as dynamic services. They can be automatically discovered and used by other services or clients. The distributed agents can collaborate and cooperate in performing a wide range of management, control and global optimization tasks using real time monitoring information. Program summaryProgram title: MonALISA Catalogue identifier: AEEZ_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEEZ_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Caltech License - free for all non-commercial activities No. of lines in distributed program, including test data, etc.: 147 802 No. of bytes in distributed program, including test data, etc.: 2 5913 689 Distribution format: tar.gz Programming language: Java, additional APIs available in Java, C, C++, Perl and python Computer: Computing Clusters, Network Devices, Storage Systems, Large scale data intensive applications Operating system: The MonALISA service is mainly used in Linux, the MonALISA client runs on all major platforms (Windows, Linux, Solaris, MacOS). Has the code been vectorized or parallelized?: It is a multithreaded application. It will efficiently use all the available processors. RAM: for the MonALISA service the minimum required memory is 64 MB; if the JVM is started allocating more memory this will be used for internal caching. The MonALISA client requires typically 256-512 MB of memory. Classification: 6.5 External routines: Requires Java: JRE or JDK to run. These external packages are used (they are included in the distribution): JINI, JFreeChart, PostgreSQL (optional). Nature of problem: To monitor and control

  13. DLTAP: A Network-efficient Scheduling Method for Distributed Deep Learning Workload in Containerized Cluster Environment

    OpenAIRE

    Qiao Wei; Li Ying; Wu Zhong-Hai

    2017-01-01

    Deep neural networks (DNNs) have recently yielded strong results on a range of applications. Training these DNNs using a cluster of commodity machines is a promising approach since training is time consuming and compute-intensive. Furthermore, putting DNN tasks into containers of clusters would enable broader and easier deployment of DNN-based algorithms. Toward this end, this paper addresses the problem of scheduling DNN tasks in the containerized cluster environment. Efficiently scheduling ...

  14. Dimension dependence of clustering dynamics in models of ballistic aggregation and freely cooling granular gas

    Science.gov (United States)

    Paul, Subhajit; Das, Subir K.

    2018-03-01

    Via event-driven molecular dynamics simulations we study kinetics of clustering in assemblies of inelastic particles in various space dimensions. We consider two models, viz., the ballistic aggregation model (BAM) and the freely cooling granular gas model (GGM), for each of which we quantify the time dependence of kinetic energy and average mass of clusters (that form due to inelastic collisions). These quantities, for both the models, exhibit power-law behavior, at least in the long time limit. For the BAM, corresponding exponents exhibit strong dimension dependence and follow a hyperscaling relation. In addition, in the high packing fraction limit the behavior of these quantities become consistent with a scaling theory that predicts an inverse relation between energy and mass. On the other hand, in the case of the GGM we do not find any evidence for such a picture. In this case, even though the energy decay, irrespective of packing fraction, matches quantitatively with that for the high packing fraction picture of the BAM, it is inversely proportional to the growth of mass only in one dimension, and the growth appears to be rather insensitive to the choice of the dimension, unlike the BAM.

  15. Dynamic Clustering-Based Estimation of Missing Values in Mixed Type Data

    Science.gov (United States)

    Ayuyev, Vadim V.; Jupin, Joseph; Harris, Philip W.; Obradovic, Zoran

    The appropriate choice of a method for imputation of missing data becomes especially important when the fraction of missing values is large and the data are of mixed type. The proposed dynamic clustering imputation (DCI) algorithm relies on similarity information from shared neighbors, where mixed type variables are considered together. When evaluated on a public social science dataset of 46,043 mixed type instances with up to 33% missing values, DCI resulted in more than 20% improved imputation accuracy over Multiple Imputation, Predictive Mean Matching, Linear and Multilevel Regression, and Mean Mode Replacement methods. Data imputed by 6 methods were used for prediction tests by NB-Tree, Random Subset Selection and Neural Network-based classification models. In our experiments classification accuracy obtained using DCI-preprocessed data was much better than when relying on alternative imputation methods for data preprocessing.

  16. Dynamical Structure of the Cross-tail Current Sheet During Substorms Observed by Cluster

    Science.gov (United States)

    Asano, Y.; Nakamura, R.; Runov, A.; Takada, T.; Baumjohann, W.; Balogh, A.; Klecker, B.; Rème, H.

    2005-12-01

    We report on the dynamical variation of the current sheet structure in the magnetotail using magnetic field and plasma data obtained by the Cluster multi-satellites. It is found that in some cases the thickness of the cross-tail current sheet shows temporal variations repeatedly. This sausage-mode-like variation is associated with substorm onsets or occurrence of fast plasma flows, with the time scale of several minutes before substorm onsets or fast flows and of a half to one minute afterwards. It frequently coexists with kink-mode-like wave or flapping motion. Such sausage-mode-like variation is mainly observed in the central part of the plasma sheet, and forms transient bifurcated currents or the intense current in the center.

  17. Clustering reveals limits of parameter identifiability in multi-parameter models of biochemical dynamics.

    Science.gov (United States)

    Nienałtowski, Karol; Włodarczyk, Michał; Lipniacki, Tomasz; Komorowski, Michał

    2015-09-29

    Compared to engineering or physics problems, dynamical models in quantitative biology typically depend on a relatively large number of parameters. Progress in developing mathematics to manipulate such multi-parameter models and so enable their efficient interplay with experiments has been slow. Existing solutions are significantly limited by model size. In order to simplify analysis of multi-parameter models a method for clustering of model parameters is proposed. It is based on a derived statistically meaningful measure of similarity between groups of parameters. The measure quantifies to what extend changes in values of some parameters can be compensated by changes in values of other parameters. The proposed methodology provides a natural mathematical language to precisely communicate and visualise effects resulting from compensatory changes in values of parameters. As a results, a relevant insight into identifiability analysis and experimental planning can be obtained. Analysis of NF-κB and MAPK pathway models shows that highly compensative parameters constitute clusters consistent with the network topology. The method applied to examine an exceptionally rich set of published experiments on the NF-κB dynamics reveals that the experiments jointly ensure identifiability of only 60% of model parameters. The method indicates which further experiments should be performed in order to increase the number of identifiable parameters. We currently lack methods that simplify broadly understood analysis of multi-parameter models. The introduced tools depict mutually compensative effects between parameters to provide insight regarding role of individual parameters, identifiability and experimental design. The method can also find applications in related methodological areas of model simplification and parameters estimation.

  18. Simplification of Water Distribution Network Simulation by Topological Clustering – Investigation of its Potential Use in Copenhagen's Water Supply Monitoring and Contamination Contingency Plans

    OpenAIRE

    Kirstein, J.K.; Albrechtsen, H.-J.; Rygaard, M.

    2014-01-01

    Topological clustering was investigated to simplify a complex water distribution network of Copenhagen, Denmark, into recogniz- able water movement patterns. This made it possible to assess the general transport of the water and to suggest strategic sampling locations. Through a topological analysis, the network model was divided into strongly and weakly connected clusters within selected time periods. Steady connected clusters were found by conducting a cluster analysis over all chosen selec...

  19. Simulations of the dissociation of small helium clusters with ab initio molecular dynamics in electronically excited states

    International Nuclear Information System (INIS)

    Closser, Kristina D.; Head-Gordon, Martin; Gessner, Oliver

    2014-01-01

    The dynamics resulting from electronic excitations of helium clusters were explored using ab initio molecular dynamics. The simulations were performed with configuration interaction singles and adiabatic classical dynamics coupled to a state-following algorithm. 100 different configurations of He 7 were excited into the 2s and 2p manifold for a total of 2800 trajectories. While the most common outcome (90%) was complete fragmentation to 6 ground state atoms and 1 excited state atom, 3% of trajectories yielded bound, He 2 * , and <0.5% yielded an excited helium trimer. The nature of the dynamics, kinetic energy release, and connections to experiments are discussed

  20. THE UNIQUE Na:O ABUNDANCE DISTRIBUTION IN NGC 6791: THE FIRST OPEN(?) CLUSTER WITH MULTIPLE POPULATIONS

    International Nuclear Information System (INIS)

    Geisler, D.; Villanova, S.; Cummings, J.; Carraro, G.; Pilachowski, C.; Johnson, C. I.; Bresolin, F.

    2012-01-01

    Almost all globular clusters investigated exhibit a spread in their light element abundances, the most studied being an Na:O anticorrelation. In contrast, open clusters show a homogeneous composition and are still regarded as Simple Stellar Populations. The most probable reason for this difference is that globulars had an initial mass high enough to retain primordial gas and ejecta from the first stellar generation and thus formed a second generation with a distinct composition, an initial mass exceeding that of open clusters. NGC 6791 is a massive open cluster and warrants a detailed search for chemical inhomogeneities. We collected high-resolution, high signal-to-noise spectra of 21 members covering a wide range of evolutionary status and measured their Na, O, and Fe content. We found [Fe/H] = +0.42 ± 0.01, in good agreement with previous values, and no evidence for a spread. However, the Na:O distribution is completely unprecedented. It becomes the first open cluster to show intrinsic abundance variations that cannot be explained by mixing, and thus the first discovered to host multiple populations. It is also the first star cluster to exhibit two subpopulations in the Na:O diagram with one being chemically homogeneous while the second has an intrinsic spread that follows the anticorrelation so far displayed only by globular clusters. NGC 6791 is unique in many aspects, displaying certain characteristics typical of open clusters, others more reminiscent of globulars, and yet others, in particular its Na:O behavior investigated here, that are totally unprecedented. It clearly had a complex and fascinating history.

  1. The Unique Na:O Abundance Distribution in NGC 6791: The First Open(?) Cluster with Multiple Populations

    Science.gov (United States)

    Geisler, D.; Villanova, S.; Carraro, G.; Pilachowski, C.; Cummings, J.; Johnson, C. I.; Bresolin, F.

    2012-09-01

    Almost all globular clusters investigated exhibit a spread in their light element abundances, the most studied being an Na:O anticorrelation. In contrast, open clusters show a homogeneous composition and are still regarded as Simple Stellar Populations. The most probable reason for this difference is that globulars had an initial mass high enough to retain primordial gas and ejecta from the first stellar generation and thus formed a second generation with a distinct composition, an initial mass exceeding that of open clusters. NGC 6791 is a massive open cluster and warrants a detailed search for chemical inhomogeneities. We collected high-resolution, high signal-to-noise spectra of 21 members covering a wide range of evolutionary status and measured their Na, O, and Fe content. We found [Fe/H] = +0.42 ± 0.01, in good agreement with previous values, and no evidence for a spread. However, the Na:O distribution is completely unprecedented. It becomes the first open cluster to show intrinsic abundance variations that cannot be explained by mixing, and thus the first discovered to host multiple populations. It is also the first star cluster to exhibit two subpopulations in the Na:O diagram with one being chemically homogeneous while the second has an intrinsic spread that follows the anticorrelation so far displayed only by globular clusters. NGC 6791 is unique in many aspects, displaying certain characteristics typical of open clusters, others more reminiscent of globulars, and yet others, in particular its Na:O behavior investigated here, that are totally unprecedented. It clearly had a complex and fascinating history.

  2. Blue straggler star populations in globular clusters. I. Dynamical properties of blue straggler stars in NGC 3201, NGC 6218, and ω Centauri

    Energy Technology Data Exchange (ETDEWEB)

    Simunovic, Mirko; Puzia, Thomas H., E-mail: msimunov@astro.puc.cl, E-mail: tpuzia@astro.puc.cl [Institute of Astrophysics, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436 Macul, Santiago (Chile)

    2014-02-10

    We present the first dynamical study of blue straggler stars (BSSs) in three Galactic globular clusters, NGC 3201, NGC 5139 (ω Cen), and NGC 6218, based on medium-resolution spectroscopy (R ≈ 10, 000) obtained with the Inamori-Magellan Areal Camera and Spectrograph mounted at the 6.5 m Baade Magellan telescope. Our BSS candidate selection technique uses HST/ACS and ESO/WFI photometric data out to >4.5 r{sub c} . We use radial velocity measurements to discard non-members and achieve a success rate of ∼93%, which yields a sample of 116 confirmed BSSs. Using the penalized pixel-fitting method (pPXF), we measure the vsin (i) values of the sample BSSs and find their distribution functions peaked at slow velocities with a long tail toward fast velocities in each globular cluster. About 90% of the BSS population in NGC 3201 and NGC 6218 exhibits values in the range 10-50 km s{sup –1}, while about 80% of the BSSs in ω Cen show vsin (i) values between 20 and 70 km s{sup –1}. We find that the BSSs in NGC 3201 and NGC 6218 that show vsin (i) > 50 km s{sup –1} are all found in the central cluster regions, inside a projected 2r{sub c} , of their parent clusters. We find a similar result in ω Cen for BSSs with vsin (i) > 70 km s{sup –1}, which are all, except for two, concentrated inside 2r{sub c} . In all globular clusters, we find rapidly rotating BSSs that have relatively high differential radial velocities that likely put them on hyperbolic orbits, suggestive of strong dynamical interactions in the past. Based on stellar spin-down and dynamical crossing timescales, we estimate that all the observed rapidly rotating BSSs are likely to form in their central cluster regions no longer than ∼300 Myr ago and may be subsequently ejected from their host globular clusters. Using dereddened V – I colors of our photometric selection, we show that blue BSSs in ω Cen with (V – I){sub 0} ≲ 0.25 mag show a significantly increased vsin (i) dispersion compared with

  3. Distributed solar radiation fast dynamic measurement for PV cells

    Science.gov (United States)

    Wan, Xuefen; Yang, Yi; Cui, Jian; Du, Xingjing; Zheng, Tao; Sardar, Muhammad Sohail

    2017-10-01

    need of complex local installations, configuring of our SRMA system is very easy. Lora also provides SRMA a means to overcome the short communication distance and weather signal propagation decline such as in ZigBee and WiFi. The host computer in SRMA system uses the low power single-board PC EMB-3870 which was produced by NORCO. Wind direction sensor SM5386B and wind-force sensor SM5387B are installed to host computer through RS-485 bus for wind reference data collection. And Davis 6450 solar radiation sensor, which is a precision instrument that detects radiation at wavelengths of 300 to 1100 nanometers, allow host computer to follow real-time solar radiation. A LoRa polling scheme is adopt for the communication between host computer and terminal nodes in SRMA. An experimental SRMA has been established. This system was tested in Ganyu, Jiangshu province from May to August, 2016. In the test, the distances between the nodes and the host computer were between 100m and 1900m. At work, SRMA system showed higher reliability. Terminal nodes could follow the instructions from host computer and collect solar radiation data of distributed PV cells effectively. And the host computer managed the SRAM and achieves reference parameters well. Communications between the host computer and terminal nodes were almost unaffected by the weather. In conclusion, the testing results show that SRMA could be a capable method for fast dynamic measuring about solar radiation and related PV cell operating characteristics.

  4. The spatial distribution of star and cluster formation in M 51

    NARCIS (Netherlands)

    Scheepmaker, R.A.; Lamers, H.J.G.L.M.; Anders, P.; Larsen, S.S.

    2009-01-01

    Aims. We study the connection between spatially resolved star formation and young star clusters across the disc of M 51. Methods. We combine star cluster data based on B, V, and I-band Hubble Space Telescope ACS imaging, together with new WFPC2 U-band photometry to derive ages, masses, and

  5. Dynamics of Surfactant Clustering at Interfaces and Its Influence on the Interfacial Tension: Atomistic Simulation of a Sodium Hexadecane-Benzene Sulfonate-Tetradecane-Water System.

    Science.gov (United States)

    Paredes, Ricardo; Fariñas-Sánchez, Ana Isabel; Medina-Rodrı Guez, Bryan; Samaniego, Samantha; Aray, Yosslen; Álvarez, Luis Javier

    2018-03-06

    The process of equilibration of the tetradecane-water interface in the presence of sodium hexadecane-benzene sulfonate is studied using intensive atomistic molecular dynamics simulations. Starting as an initial point with all of the surfactants at the interface, it is obtained that the equilibration time of the interface (several microseconds) is orders of magnitude higher than previously reported simulated times. There is strong evidence that this slow equilibration process is due to the aggregation of surfactants molecules on the interface. To determine this fact, temporal evolution of interfacial tension and interfacial formation energy are studied and their temporal variations are correlated with cluster formation. To study cluster evolution, the mean cluster size and the probability that a molecule of surfactant chosen at random is free are obtained as a function of time. Cluster size distribution is estimated, and it is observed that some of the molecules remain free, whereas the rest agglomerate. Additionally, the temporal evolution of the interfacial thickness and the structure of the surfactant molecules on the interface are studied. It is observed how this structure depends on whether the molecules agglomerate or not.

  6. Clustering and Bayesian hierarchical modeling for the definition of informative prior distributions in hydrogeology

    Science.gov (United States)

    Cucchi, K.; Kawa, N.; Hesse, F.; Rubin, Y.

    2017-12-01

    In order to reduce uncertainty in the prediction of subsurface flow and transport processes, practitioners should use all data available. However, classic inverse modeling frameworks typically only make use of information contained in in-situ field measurements to provide estimates of hydrogeological parameters. Such hydrogeological information about an aquifer is difficult and costly to acquire. In this data-scarce context, the transfer of ex-situ information coming from previously investigated sites can be critical for improving predictions by better constraining the estimation procedure. Bayesian inverse modeling provides a coherent framework to represent such ex-situ information by virtue of the prior distribution and combine them with in-situ information from the target site. In this study, we present an innovative data-driven approach for defining such informative priors for hydrogeological parameters at the target site. Our approach consists in two steps, both relying on statistical and machine learning methods. The first step is data selection; it consists in selecting sites similar to the target site. We use clustering methods for selecting similar sites based on observable hydrogeological features. The second step is data assimilation; it consists in assimilating data from the selected similar sites into the informative prior. We use a Bayesian hierarchical model to account for inter-site variability and to allow for the assimilation of multiple types of site-specific data. We present the application and validation of the presented methods on an established database of hydrogeological parameters. Data and methods are implemented in the form of an open-source R-package and therefore facilitate easy use by other practitioners.

  7. Network Signaling Channel for Improving ZigBee Performance in Dynamic Cluster-Tree Networks

    Directory of Open Access Journals (Sweden)

    D. Hämäläinen

    2008-03-01

    Full Text Available ZigBee is one of the most potential standardized technologies for wireless sensor networks (WSNs. Yet, sufficient energy-efficiency for the lowest power WSNs is achieved only in rather static networks. This severely limits the applicability of ZigBee in outdoor and mobile applications, where operation environment is harsh and link failures are common. This paper proposes a network channel beaconing (NCB algorithm for improving ZigBee performance in dynamic cluster-tree networks. NCB reduces the energy consumption of passive scans by dedicating one frequency channel for network beacon transmissions and by energy optimizing their transmission rate. According to an energy analysis, the power consumption of network maintenance operations reduces by 70%–76% in dynamic networks. In static networks, energy overhead is negligible. Moreover, the service time for data routing increases up to 37%. The performance of NCB is validated by ns-2 simulations. NCB can be implemented as an extension on MAC and NWK layers and it is fully compatible with ZigBee.

  8. Phase Diagram and Sweep Dynamics of a One-Dimensional Generalized Cluster Model

    Science.gov (United States)

    Ohta, Takumi; Tanaka, Shu; Danshita, Ippei; Totsuka, Keisuke

    2015-06-01

    We numerically study quantum phase transitions and dynamical properties in the one-dimensional cluster model with several interactions by using the time-evolving block decimation method for infinite systems and the exact diagonalization. First, boundaries among several quantum phases of the model are determined from energy gap and each phase is characterized by order parameters and the entanglement spectrum (ES). We confirm that in the model with open boundary condition the degeneracy of the lowest levels in the ES corresponds to that of the ground states. Then, using the time-dependent Bogoliubov transformation with open boundary condition, we investigate dynamical properties during an interaction sweep through the critical point which separates two topological phases involving four-fold degeneracy in the ground state. After a slow sweep across the critical point, we observe spatially periodic structures in the string correlation functions and the entanglement entropy. It is shown that the periodicities stem from the Bogoliubov quasiparticles generated near the critical point.

  9. Theoretical studies of zirconium and carbon clusters with molecular dynamics simulations

    International Nuclear Information System (INIS)

    Zhang, B.

    1993-08-01

    In this dissertation, we will present a systematic study of structures of fullerenes ranging from C 20 to C 100 by introducing a novel scheme. Using our new scheme, we not only reproduce all known fullerene structures but also successfully predicted several other fullerene structures which were confirmed by experiments. By utilizing the tight-binding molecular-dynamic (TBMD) simulation, we also studied the dynamical behavior of fullerenes: Vibrations, thermal disintegration of individual clusters as well as collisions between fullerenes. If the beauty of carbon fullerene is not enough, people found that carbon can also form tubules and even speculated that they can form three-dimensional graphite-like networks. By extending our fullerene structure searching scheme, we performed a search for the ground-state structure of three dimensional carbon network. We found the most stable structure people ever proposed for simple cubic based networks. From the difference of this new form of carbon and graphite in the electronic and vibrational properties, we propose an experimental probe to identify these novel three-dimensional carbon networks

  10. An adaptive clustering approach to dynamic load balancing and energy efficiency in wireless sensor networks

    International Nuclear Information System (INIS)

    Gherbi, Chirihane; Aliouat, Zibouda; Benmohammed, Mohamed

    2016-01-01

    Clustering is a well known approach to cope with large nodes density and efficiently conserving energy in Wireless Sensor Networks (WSN). Load balancing is an effective approach for optimizing resources like channel bandwidth, the main objective of this paper is to combine these two valuable approaches in order to significantly improve the main WSN service such as information routing. So, our proposal is a routing protocol in which load traffic is shared among cluster members in order to reduce the dropping probability due to queue overflow at some nodes. To this end, a novel hierarchical approach, called Hierarchical Energy-Balancing Multipath routing protocol for Wireless Sensor Networks (HEBM) is proposed. The HEBM approach aims to fulfill the following purposes: decreasing the overall network energy consumption, balancing the energy dissipation among the sensor nodes and as direct consequence: extending the lifetime of the network. In fact, the cluster-heads are optimally determined and suitably distributed over the area of interest allowing the member nodes reaching them with adequate energy dissipation and appropriate load balancing utilization. In addition, nodes radio are turned off for fixed time duration according to sleeping control rules optimizing so their energy consumption. The performance evaluation of the proposed protocol is carried out through the well-known NS2 simulator and the exhibited results are convincing. Like this, the residual energy of sensor nodes was measured every 20 s throughout the duration of simulation, in order to calculate the total number of alive nodes. Based on the simulation results, we concluded that our proposed HEBM protocol increases the profit of energy, and prolongs the network lifetime duration from 32% to 40% compared to DEEAC reference protocol and from 25% to 28% compared to FEMCHRP protocol. The authors also note that the proposed protocol is 41.7% better than DEEAC with respect to FND (Fist node die), and 25

  11. Spectroscopic characterization of galaxy clusters in RCS-1: spectroscopic confirmation, redshift accuracy, and dynamical mass-richness relation

    Science.gov (United States)

    Gilbank, David G.; Barrientos, L. Felipe; Ellingson, Erica; Blindert, Kris; Yee, H. K. C.; Anguita, T.; Gladders, M. D.; Hall, P. B.; Hertling, G.; Infante, L.; Yan, R.; Carrasco, M.; Garcia-Vergara, Cristina; Dawson, K. S.; Lidman, C.; Morokuma, T.

    2018-05-01

    We present follow-up spectroscopic observations of galaxy clusters from the first Red-sequence Cluster Survey (RCS-1). This work focuses on two samples, a lower redshift sample of ˜30 clusters ranging in redshift from z ˜ 0.2-0.6 observed with multiobject spectroscopy (MOS) on 4-6.5-m class telescopes and a z ˜ 1 sample of ˜10 clusters 8-m class telescope observations. We examine the detection efficiency and redshift accuracy of the now widely used red-sequence technique for selecting clusters via overdensities of red-sequence galaxies. Using both these data and extended samples including previously published RCS-1 spectroscopy and spectroscopic redshifts from SDSS, we find that the red-sequence redshift using simple two-filter cluster photometric redshifts is accurate to σz ≈ 0.035(1 + z) in RCS-1. This accuracy can potentially be improved with better survey photometric calibration. For the lower redshift sample, ˜5 per cent of clusters show some (minor) contamination from secondary systems with the same red-sequence intruding into the measurement aperture of the original cluster. At z ˜ 1, the rate rises to ˜20 per cent. Approximately ten per cent of projections are expected to be serious, where the two components contribute significant numbers of their red-sequence galaxies to another cluster. Finally, we present a preliminary study of the mass-richness calibration using velocity dispersions to probe the dynamical masses of the clusters. We find a relation broadly consistent with that seen in the local universe from the WINGS sample at z ˜ 0.05.

  12. Spectroscopic Characterisation of Galaxy Clusters in RCS-1: spectroscopic confirmation, redshift accuracy, and dynamical mass-richness relation

    Science.gov (United States)

    Gilbank, David G.; Felipe Barrientos, L.; Ellingson, Erica; Blindert, Kris; Yee, H. K. C.; Anguita, T.; Gladders, M. D.; Hall, P. B.; Hertling, G.; Infante, L.; Yan, R.; Carrasco, M.; Garcia-Vergara, Cristina; Dawson, K. S.; Lidman, C.; Morokuma, T.

    2018-02-01

    We present follow-up spectroscopic observations of galaxy clusters from the first Red-sequence Cluster Survey (RCS-1). This work focuses on two samples, a lower redshift sample of ˜30 clusters ranging in redshift from z˜0.2-0.6 observed with multi-object spectroscopy (MOS) on 4-6.5-m class telescopes and a z˜1 sample of ˜10 clusters 8-m class telescope observations. We examine the detection efficiency and redshift accuracy of the now widely-used red-sequence technique for selecting clusters via overdensities of red-sequence galaxies. Using both these data and extended samples including previously-published RCS-1 spectroscopy and spectroscopic redshifts from SDSS, we find that the red-sequence redshift using simple two-filter cluster photometric redshifts is accurate to σz ≈ 0.035(1 + z) in RCS-1. This accuracy can potentially be improved with better survey photometric calibration. For the lower redshift sample, ˜5% of clusters show some (minor) contamination from secondary systems with the same red-sequence intruding into the measurement aperture of the original cluster. At z˜1 the rate rises to ˜20%. ˜10% of projections are expected to be serious, where the two components contribute significant numbers of their red-sequence galaxies to another cluster. Finally, we present a preliminary study of the mass-richness calibration using velocity dispersions to probe the dynamical masses of the clusters. We find a relation broadly consistent with that seen in the local universe from the WINGS sample at z˜0.05.

  13. Investigating the effect of external trauma through a dynamic system modeling approach for clustering causality in diabetic foot ulcer development.

    Science.gov (United States)

    Salimi, Parisa; Hamedi, Mohsen; Jamshidi, Nima; Vismeh, Milad

    2017-04-01

    Diabetes and its associated complications are realized as one of the most challenging medical conditions threatening more than 29 million people only in the USA. The forecasts suggest a suffering of more than half a billion worldwide by 2030. Amid all diabetic complications, diabetic foot ulcer (DFU) has attracted much scientific investigations to lead to a better management of this disease. In this paper, a system thinking methodology is adopted to investigate the dynamic nature of the ulceration. The causal loop diagram as a tool is utilized to illustrate the well-researched relations and interrelations between causes of the DFU. The result of clustering causality evaluation suggests a vicious loop that relates external trauma to callus. Consequently a hypothesis is presented which localizes development of foot ulceration considering distribution of normal and shear stress. It specifies that normal and tangential forces, as the main representatives of external trauma, play the most important role in foot ulceration. The evaluation of this hypothesis suggests the significance of the information related to both normal and shear stress for managing DFU. The results also discusses how these two react on different locations on foot such as metatarsal head, heel and hallux. The findings of this study can facilitate tackling the complexity of DFU problem and looking for constructive mitigation measures. Moreover they lead to developing a more promising methodology for managing DFU including better prognosis, designing prosthesis and insoles for DFU and patient caring recommendations. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Re-solution of xenon clusters in plutonium dioxide under the collision cascade impact: A molecular dynamics simulation

    Science.gov (United States)

    Seitov, D. D.; Nekrasov, K. A.; Kupryazhkin, A. Ya.; Gupta, S. K.; Akilbekov, A. T.

    2017-09-01

    The interaction of xenon clusters with the collision cascades in the PuO2 crystals is investigated using the molecular dynamics simulation and the approximation of the pair interaction potentials. The potentials of interaction of Xe atoms with the surrounding particles in the crystal lattice are suggested, that are valid in the range of high collision energies. The cascades created by the recoil 235U ions formed as the plutonium α-decay product are considered, and the influence of such cascades on the structure of the xenon clusters is analyzed. It is shown, that the cascade-cluster interaction leads to release of the xenon atoms from the clusters and their subsequent re-solution in the crystal bulk.

  15. Resolving the anomalous infrared spectrum of the MeCN-HCl molecular cluster using ab Initio molecular dynamics

    DEFF Research Database (Denmark)

    Bork, Nicolai Christian; Loukonen, Ville; Kjærgaard, Henrik Grum

    2014-01-01

    We present a molecular dynamics (MD) based study of the acetonitrile-hydrogen chloride molecular cluster in the gas phase, aimed at resolving the anomalous features often seen in infrared spectra of hydrogen bonded complexes. We find that the infrared spectrum obtained from the Fourier transform...

  16. Molecular dynamics simulation investigations of H2/D2 dissocitive chemisorption dynamics on Cun(n=13-14) Rigid/nonrigid clusters

    International Nuclear Information System (INIS)

    Elzein, N.

    2004-01-01

    In this work with a use of molecular dynamic simulations we have reported the results of a quasiclassical simulation study of the interaction of H2/(D2) with Cu N (N=13-14) atoms in both rigid /(non rigid) clusters.The geometry of the cluster is obtained by an embedded-atom (EA) mode potential, and the interaction between the molecule and cIuster is described by a LEPS -London-Eyring -Polanyi-Sato) potential energy function.Both channels the reactive dissociative adsorption of the molecule on the cIuster) and non reactive (scattering of the molecule from the cluster) are considered. The dissociative chemisorption probability, cross section and rate constant are studied as functions of the initial quantal rovibrational state of the molecule, collision energy, impact parameter and the temperature (OK,296K,834K ,1014K,1554K) of the clusters

  17. Dynamic Cooperative Clustering Based Power Assignment: Network Capacity and Lifetime Efficient Topology Control in Cooperative Ad Hoc Networks

    Directory of Open Access Journals (Sweden)

    Xiao-Hong Li

    2014-01-01

    Full Text Available Cooperative communication (CC is used in topology control as it can reduce the transmission power and expand the transmission range. However, all previous research on topology control under the CC model focused on maintaining network connectivity and minimizing the total energy consumption, which would lead to low network capacity, transmission interruption, or even network paralysis. Meanwhile, without considering the balance of energy consumption in the network, it would reduce the network lifetime and greatly affect the network performance. This paper tries to solve the above problems existing in the research on topology control under the CC model by proposing a power assignment (DCCPA algorithm based on dynamic cooperative clustering in cooperative ad hoc networks. The new algorithm clusters the network to maximize network capacity and makes the clusters communicate with each other by CC. To reduce the number of redundant links between clusters, we design a static clustering method by using Kruskal algorithm. To maximize the network lifetime, we also propose a cluster head rotating method which can reach a good tradeoff between residual energy and distance for the cluster head reselection. Experimental results show that DCCPA can improve 80% network capacity with Cooperative Bridges algorithm; meanwhile, it can improve 20% network lifetime.

  18. Temperature-associated dynamics of songbird winter distributions and abundances.

    Science.gov (United States)

    Butler, J Russell; MacMynowski, Dena P; Laurent, Chad; Root, Terry L

    2007-12-01

    Using Christmas Bird Count data, we analyze the annual spatio-temporal abundances of six passerine species in the upper Great Plains, US (1960-1990). This study provides new insight into how global warming could cause separation of species within present-day communities. We find that winter relative abundances of similarly-sized songbirds are differentially affected by ambient winter temperature. As such, average annual winter temperature fluctuations (i.e., severity of winter) are significantly (P < 0.05) correlated with the relative abundances of three species while the other three are not. Our conditional probability-of-occurrence analysis indicates that the abundances of the three temperature-associated species declined markedly below -4 degrees C while the abundances of the other three species fluctuated little from 8 degrees C to -16 degrees C. We conclude that even in colder climates i) the winter distributions of some, but not all, songbirds are directly or indirectly limited by temperature; and ii) these birds have dynamic abundances that can quickly respond to temperature changes.

  19. An evaluation of biosurveillance grid--dynamic algorithm distribution across multiple computer nodes.

    Science.gov (United States)

    Tsai, Ming-Chi; Tsui, Fu-Chiang; Wagner, Michael M

    2007-10-11

    Performing fast data analysis to detect disease outbreaks plays a critical role in real-time biosurveillance. In this paper, we described and evaluated an Algorithm Distribution Manager Service (ADMS) based on grid technologies, which dynamically partition and distribute detection algorithms across multiple computers. We compared the execution time to perform the analysis on a single computer and on a grid network (3 computing nodes) with and without using dynamic algorithm distribution. We found that algorithms with long runtime completed approximately three times earlier in distributed environment than in a single computer while short runtime algorithms performed worse in distributed environment. A dynamic algorithm distribution approach also performed better than static algorithm distribution approach. This pilot study shows a great potential to reduce lengthy analysis time through dynamic algorithm partitioning and parallel processing, and provides the opportunity of distributing algorithms from a client to remote computers in a grid network.

  20. An Evaluation of Biosurveillance Grid—Dynamic Algorithm Distribution Across Multiple Computer Nodes

    Science.gov (United States)

    Tsai, Ming-Chi; Tsui, Fu-Chiang; Wagner, Michael M.

    2007-01-01

    Performing fast data analysis to detect disease outbreaks plays a critical role in real-time biosurveillance. In this paper, we described and evaluated an Algorithm Distribution Manager Service (ADMS) based on grid technologies, which dynamically partition and distribute dete